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Algebra

Class 9th Mathematics Term 1 Tamilnadu Board Solution
Exercise 3.1
  1. State whether the following expressions are polynomials in one variable or not.…
  2. Write the coefficient of x^2 and x in each of the following i. 2 + 3x - 4x^2 +…
  3. Write the degree of each of the following polynomials. i. 4 - 3x^2 ii. 5y + √2…
  4. Classify the following polynomials based on their degree. i. 3x^2 + 2x + 1 ii.…
  5. Give one example of a binomial of degree 27 and monomial of degree 49 and…
Exercise 3.2
  1. Find the zeros of the following polynomials. i. p(x)= 4x - 1 ii. p(x) = 3x + 5…
  2. Find the roots of the following polynomial equations. i. x - 3 = 0 ii. 5x - 6 =…
  3. x^2 - 5x + 6 = 0; x = 2, 3 Verify Whether the following are roots of the…
  4. x^2 + 4x + 3 = 0; x = −1, 2 Verify Whether the following are roots of the…
  5. x^3 - 2x^2 - 5x + 6 = 0; x = 1, −2, 3 Verify Whether the following are roots of…
  6. x^3 - 2x^2 - x + 2 = 0; x = −1, 2, 3 Verify Whether the following are roots of…
Exercise 3.3
  1. (5x^3 - 8x^2 + 5x - 7) ÷ (x - 1) Find the quotient the and remainder of the…
  2. (2x^2 - 3x - 14) ÷ (x + 2) Find the quotient the and remainder of the following…
  3. (9 + 4x + 5x^2 + 3x^3) ÷ (x+ 1) Find the quotient the and remainder of the…
  4. (4x^3 - 2x^2 + 6x + 7) ÷ (3 + 2x) Find the quotient the and remainder of the…
  5. (−18 - 9x + 7x^2) ÷ (x - 2) Find the quotient the and remainder of the…
Exercise 3.4
  1. 3x^3 + 4x^2 - 5x + 8 is divided by x - 1 Find the remainder using remainder…
  2. 5x^3 + 2x^2 - 6x + 12 is divided by x + 2 Find the remainder using remainder…
  3. 2x^3 - 4x^2 + 7x + 6 is divided by x - 2 Find the remainder using remainder…
  4. 4x^3 - 3x^2 + 2x - 4 is divided by x + 3 Find the remainder using remainder…
  5. 4x^3 - 12x^2 + 11x - 5 is divided by 2x - 1 Find the remainder using remainder…
  6. 8x^4 + 12x^3 - 2x^2 - 18x + 14 is divided by x + 1 Find the remainder using…
  7. x^3 - ax^2 - 5x + 2a is divided by x - a Find the remainder using remainder…
  8. When the polynomial 2x^3 - 2x^2 + 9x - 8 is divided by x - 3 the remainder is…
  9. Find the value of m if x^3 - 6x^2 + mx + 60 leaves the remainder 2 when divided…
  10. If (x - 1) divides mx^3 - 2x^2 + 25x - 26 without remainder find the value of m…
  11. If the polynomials x^3 + 3x^2 - m and 2x^3 - mx + 9 leaves the same remainder…
Exercise 3.5
  1. 6x^4 + 7x^3 - 5x - 4 Determine whether (x + 1) is a factor of the following…
  2. 2x^4 + 9x^3 + 2x^2 + 10x + 15 Determine whether (x + 1) is a factor of the…
  3. 3x^3 + 8x^2 + 6x - 5 Determine whether (x + 1) is a factor of the following…
  4. x^3 - 14x^2 + 3x + 12 Determine whether (x + 1) is a factor of the following…
  5. Determine whether (x + 4) is a factor of x^3 + 3x^2 - 5x + 36.
  6. Using factor theorem show that (x - 1) is a factor of 4x^3 - 6x^2 + 9x - 7.…
  7. Determine whether (2x + 1) is a factor of 4x^3 + 4x^2 - x - 1.
  8. Determine the value of p if (x + 3) is a factor of x^3 - 3x^2 - px + 24.…
Exercise 3.6
  1. The coefficient of x^2 x in 2x^3 - 3x^2 - 2x + 3 are respectively:A. 2, 3 B. -…
  2. The degree of polynomial 4x^2 - 7x^3 + 6x + 1 is:A. 2 B. 1 C. 3 D. 0…
  3. The polynomial 3x - 2 is a :A. Linear polynomial B. Quadratic polynomial C.…
  4. The polynomial 4x^2 + 2x - 2 is a :A. Linear polynomial B. Quadratic polynomial…
  5. The zero of the polynomial 2x - 5:A. 5/2 B. - 5/2 C. 2/5 D. - 2/5…
  6. The root of polynomial equation 3x - 1 is:A. - 1/3 B. 1/3 C. 1 D. 3…
  7. The root of polynomial equation x^2 + 2x = 0:A. 0, 2 B. 1, 2 C. 1, - 2 D. 0, - 2…
  8. If a polynomial p(x) is divided by (ax + b), then the remainder is:A. p(b/a) B.…
  9. If a polynomial x^3 - ax^2 + ax - a is divided by (x - a), then the remainder…
  10. If (ax - b) is a factor of p(x) then,A. p(b) = 0 B. p(- b/a) = 0 C. p(a) = 0 D.…
  11. One of the factor of x^2 - 3x - 10 is :A. x - 2 B. x + 5 C. x - 5 D. x - 3…
  12. One of the factor of x^3 - 2x^2 + 2x - 1 is :A. x - 1 B. x + 1 C. x - 2 D. x +…

Exercise 3.1
Question 1.

State whether the following expressions are polynomials in one variable or not. Give reasons for your answer.

i. 2x5 – x3 + x – 6

ii. 3x2 – 2x + 1

iii. y3 + 2√3

iv.

v.

vi. x3 + y3 + z6


Answer:

i. 2x5 – x3 + x – 6


There is only one variable ‘x’ with whole number power. So, this is polynomial in one variable.


ii. 3x2 – 2x + 1


There is only one variable ‘x’ with whole number power. So, this is polynomial in one variable.


iii. y3 + 2√3


There is only one variable ‘y’ with whole number power. So, this is polynomial in one variable.


iv.



There is only one variable ‘x’ with whole number power. So, this is polynomial in one variable.


v. 3√ t + 2t


There is only one variable ‘t’ but in 3√t, power of t is which is not a whole number. So, this is not a polynomial in one variable.


vi. x3 + y3 + z3


There are three variables x, y and z, but power is whole number. So, this is not a polynomial in one variable.



Question 2.

Write the coefficient of x2 and x in each of the following

i. 2 + 3x – 4x2 + x3

ii. √3 x + 1

iii. x3 + √2 x2 + 4x – 1

iv.


Answer:

i 2 + 3x – 4x2 + x3


Co-efficient of x2 = -4


Co-efficient of x = 3


ii √3x + 1


Co-efficient of x2 = 0


Co-efficient of x = √3


iii x3 + √2x2 + 4x – 1


Co-efficient of x2 = √2


Co-efficient of x = 4


iv



= x2 + 3x + 6 = 0


Co-efficient of x2 = 1


Co-efficient of x = 3



Question 3.

Write the degree of each of the following polynomials.

i. 4 – 3x2

ii. 5y + √2

iii. 12 – x + 4x3

iv. 5


Answer:

i. 4 – 3x2


Degree of the polynomial = 2


ii. 5y + √2


Degree of the polynomial = 1


iii. 12 – x + 4x3


Degree of the polynomial = 3


iv. 5


Degree of the polynomial = 0



Question 4.

Classify the following polynomials based on their degree.

i. 3x2 + 2x + 1

ii. 4x3 – 1

iii. y + 3

iv. y2 – 4

v. 4x3

vi. 2x


Answer:

i. 3x2 + 2x +1


Since, the highest degree of polynomial is 2


It is a quadratic polynomial.


ii. 4x3 – 1


Since, the highest degree of polynomial is 3.


It is a cubic polynomial.


iii. y + 3


Since, the highest degree of polynomial is 1


It is a linear polynomial


iv. y2 – 4


Since, the highest degree of polynomial is 2


It is a quadratic polynomial.


v. 4x3


Since, the highest degree of polynomial is 3.


It is a cubic polynomial.


vi. 2x


Since, the highest degree of polynomial is 1


It is a linear polynomial



Question 5.

Give one example of a binomial of degree 27 and monomial of degree 49 and trinomial of degree 36.


Answer:

Binomial means having two terms. So binomial of degree 27 is x27 + y.


Monomial means having one term. So, monomial of degree is x49.


Trinomial means having three term. So, trinomial of degree is x36 + y + 2.




Exercise 3.2
Question 1.

Find the zeros of the following polynomials.

i. p(x)= 4x – 1

ii. p(x) = 3x + 5

iii. p(x) = 2x

v. p(x) = x + 9


Answer:

i. p(x) = 4x – 1





Hence, is the zero of p(x).


ii. p(x) = 3x + 5





Hence, is the zero of p(x).


iii. p(x) = 2x


p(0) = 2(0) = 0


Hence, 0 is the zero of p(x).


iv. p(x) = x + 9


p(-9) = -9 + 9 = 0


Hence, -9 is the zero of p(x).



Question 2.

Find the roots of the following polynomial equations.

i. x – 3 = 0

ii. 5x – 6 = 0

iii. 11x + 1 = 0

iv. −9x = 0


Answer:

i. x – 5 = 0


⇒ x = 5


∴ x = 5 is a root of x – 5 = 0


ii. 5x – 6 = 0


⇒ 5x = 6



is a root of 5x – 6 = 0


iii. 11x + 1 = 0


⇒ 11x = -1



is a root of 11x + 1 = 0.


iv. -9x = 0



⇒ x = 0


∴ x = 0 is a root of -9x = 0.



Question 3.

Verify Whether the following are roots of the polynomial equations indicated against them.

x2 – 5x + 6 = 0; x = 2, 3


Answer:

x2 – 5x + 6 = 0


Let p(x) = x2 – 5x + 6


p(2) = (2)2 – 5(2) + 6


= 4 – 10 + 6


= 10 – 10 = 0


∴ x = 2 is a root of x2 – 5x + 6 = 0


p(x) = x2 – 5x + 6


p(3) = (3)2 – 5(3) + 6


= 9 – 15 + 6


= 15 – 15 = 0


∴ x = 3 is a root of x2 – 5x + 6 = 0



Question 4.

Verify Whether the following are roots of the polynomial equations indicated against them.

x2 + 4x + 3 = 0; x = −1, 2


Answer:

x2 + 4x + 3 = 0


let p(x) = x2 + 4x + 3


p(-1) = (-1)2 + 4(-1) + 3


= 1 – 4 + 3


= 4 – 4 = 0


∴ x = -1 is a root of x2 + 4x + 3 = 0


p(x) = x2 + 4x + 3 = 0


p(2) = (2)2 + 4(2) + 3


= 4 + 8 + 3


= 11 + 4 = 15 ≠ 0


∴ x = 2 is not a root of x2 + 4x + 3 = 0.



Question 5.

Verify Whether the following are roots of the polynomial equations indicated against them.

x3 – 2x2 – 5x + 6 = 0; x = 1, −2, 3


Answer:

x3 – 2x2 – 5x + 6 = 0


let p(x) = x3 – 2x2 – 5x + 6


p(1) = (1)3 – 2(1)2 – 5(1) + 6


= 1 – 2 × 1 – 5 + 6


= 1 – 2 – 5 + 6


= 7 – 7 = 0


∴ x = 1 is a root of x3 – 2x2 – 5x + 6 = 0.


p(x) = x3 – 2x2 – 5x + 6


p(-2) = (-2)3 – 2(-2)2 – 5(-2) + 6


= -8 – 2 × 4 – 5 × 2 + 6


= -8 – 8 + 10 + 6


= -16 + 16 = 0


∴ x = -2 is a root of x3 – 2x2 – 5x + 6 = 0.


p(x) = x3 – 2x2 – 5x + 6 = 0


p(3) = (3)3 – 2(3)2 – 5(3) + 6


= 27 – 2 × 9 – 5 × 3 + 6


= 27 – 18 – 15 + 6


= 33 – 33 = 0


∴ x = 3 is a root of x3 – 2x2 – 5x + 6 = 0.



Question 6.

Verify Whether the following are roots of the polynomial equations indicated against them.

x3 – 2x2 – x + 2 = 0; x = −1, 2, 3


Answer:

x3 – 2x2 – x + 2 = 0


p(x) = x3 – 2x2 – x + 2 = 0


p(-1) = (-1)3 – 2(-1)2 - (-1) + 2


= -1 – 2 × 1 + 1 + 2


= -1 – 2 + 1 + 2


= -3 + 3 = 0


∴ x = -1 is a root of x3 – 2x2 – x + 2 = 0


p(x) = x3 – 2x2 – x + 2 = 0


p(2) = (2)3 – 2(2)2 – (2) + 2


= 8 – 2 × 4 – 2 + 2


= 8 – 8 – 2 + 2


= 10 – 10 = 0


∴ x = 2 is a root of x3 – 2x2 – x + 2 = 0.


p(x) = x3 – 2x2 – x + 2 = 0


p(3) = (3)3 – 2(3)2 – (3) + 2


= 27 – 2 × 9 – 3 + 2


= 27 – 18 – 3 + 2


= 29 – 21 = 8 ≠ 0


∴ x = 3 is not a root of x3 – 2x2 – x + 2 = 0.




Exercise 3.3
Question 1.

Find the quotient the and remainder of the following division.

(5x3 – 8x2 + 5x – 7) ÷ (x – 1)


Answer:

(5x3 – 8x2 + 5x – 7) ÷ (x – 1)

We see that the equation is already arranged in descending order.


Now we need to divide (5x3 – 8x2 + 5x – 7) by (x – 1).


Now we need to find out by how much should we multiple “x” to get a value as much as 5x3.


To get x3, we need to multiply x×x2.


Therefore, we need to multiply with 5x2 × (x – 1) and we get (5x3 – 5x2) now subtract (5x3 – 5x2) from 5x3 – 8x2 + 5x – 7 so we get – 3x2.


Now we carry 5x – 7 along with – 3x2, as shown below


So, in same way we have keep dividing till we get rid of x as shown below.



here (x – 1) × (– 3x)


= – 3x2 + 3x


here (x – 1) × 2


= 2x – 2


Therefore, we got the quotient = 5x2 – 3x + 2 and


Remainder = –5



Question 2.

Find the quotient the and remainder of the following division.

(2x2 – 3x – 14) ÷ (x + 2)


Answer:

(2x2 – 3x – 14) ÷ (x + 2)


We see that the equation is already arranged in descending order.


Now we need to divide (2x2 – 3x – 14) by (x + 2).


Now we need to find out by how much should we multiple “x” to get a value as much as 2x2.


To get x2, we need to multiply x×x.


Therefore, we need to multiply with 2x × (x + 2) and we get (2x2 + 4x) now subtract (2x2 + 4x) from 2x2 – 3x – 14 so we get –7x.


Now we carry 14 along with –7x, as shown below


So, in same way we have keep dividing till we get rid of x as shown below.



here (x + 2) × (– 7)


= – 7x – 14


Therefore, we got the quotient = 2x – 7 and


Remainder = 0



Question 3.

Find the quotient the and remainder of the following division.

(9 + 4x + 5x2 + 3x3) ÷ (x+ 1)


Answer:

(9 + 4x + 5x2 + 3x3) ÷ (x + 1)


We see that the equation is not arranged in descending order, so we need first arrange it in descending order of the power of x.


Therefore it becomes,


(3x3 + 5x2 + 4x + 9) ÷ (x + 1)


Now we need to divide (3x3 + 5x2 + 4x + 9) by (x + 1).


Now we need to find out by how much should we multiple “x” to get a value as much as 3x3.


To get x3, we need to multiply x×x2.


Therefore, we need to multiply with 3x2 × (x + 1) and we get (3x3 + 3x2) now subtract (3x3 + 3x2) from 3x3 + 5x2 + 4x + 9 so we get 2x2.


Now we carry 4x + 9 along with 2x2, as shown below


So, in same way we have keep dividing till we get rid of x as shown below.



here (x + 1) × ( 2x)


= 2x2 + 2x


here (x + 1) × 2


= 2x + 2


Therefore, we got the quotient = 3x2 + 2x + 2 and


Remainder = 7



Question 4.

Find the quotient the and remainder of the following division.

(4x3 – 2x2 + 6x + 7) ÷ (3 + 2x)


Answer:

(4x3 – 2x2 + 6x + 7) ÷ (3 + 2x)


We see that the equation is not arranged in descending order, so we need first arrange it in descending order of the power of x.


Therefore it becomes,


(4x3 – 2x2 + 6x + 7) ÷ (2x + 3)


Now we need to divide (4x3 – 2x2 + 6x + 7) by (2x + 3)


Now we need to find out by how much should we multiple “x” to get a value as much as 4x3.


To get x3, we need to multiply x×x2.


Therefore we need to multiply with 2x2 × (2x + 3) and we get (4x3 + 6x2) now subtract (4x3 + 6x2) from 4x3 – 2x2 + 6x + 7so we get – 8x2.


Now we carry 6x + 7along with 4x2, as shown below


So, in same way we have keep dividing till we get rid of x as shown below.



here (2x + 3) × (–4x)


= – 8x2 – 12x


here (2x + 3) × 9


= 18x + 27


Therefore, we got the quotient = 2x2 – 4x + 9 and


Remainder = –20



Question 5.

Find the quotient the and remainder of the following division.

(−18 – 9x + 7x2) ÷ (x – 2)


Answer:

(−18 – 9x + 7x2) ÷ (x – 2)


We see that the equation is not arranged in descending order, so we need first arrange it in descending order of the power of x.


Therefore it becomes,


(7x2 – 9x – 18) ÷ (x – 2)


Now we need to divide (7x2 – 9x – 18) by (x – 2).


Now we need to find out by how much should we multiple “x” to get a value as much as 7x2.


To get x2, we need to multiply x×x.


Therefore, we need to multiply with 7x × (x – 2) and we get (7x2 – 14x) now subtract (7x2 – 14x) from 7x2 – 9x – 18 so we get 5x.


Now we carry 18 along with 5x, as shown below


So, in same way we have keep dividing till we get rid of x as shown below.



here (x – 2) × 5


= 5x – 10


Therefore, we got the quotient = 7x + 5 and


Remainder = – 8




Exercise 3.4
Question 1.

Find the remainder using remainder theorem, when

3x3 + 4x2 – 5x + 8 is divided by x – 1


Answer:

3x3 + 4x2 – 5x + 8 is divided by x – 1


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 3x3 + 4x2 – 5x + 8 and we have (x – 1)


The zero of (x – 1) is 1


Now using Remainder theorem,


p(x) = 3x3 + 4x2 – 5x + 8 is divided by x – 1 then, p(1) is the remainder


p(1) = 3(1)3 + 4(1)2 – 5(1) + 8


= 3 + 4 – 5 + 8


= 10


Remainder = 10



Question 2.

Find the remainder using remainder theorem, when

5x3 + 2x2 – 6x + 12 is divided by x + 2


Answer:

5x3 + 2x2 – 6x + 12 is divided by x + 2


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 5x3 + 2x2 – 6x + 12 and we have (x + 2)


The zero of (x + 2) is – 2


Now using Remainder theorem,


p(x) = 5x3 + 2x2 – 6x + 12 is divided by x + 2 then, p(–2) is the remainder


p(–2) = 5(–2)3 + 2(–2)2 – 6(–2) + 12


= 5×(–8) + 2×4 – (– 12) + 12


= – 40 + 8 + 12 + 12


= – 40 + 32


= – 8


Remainder = –8



Question 3.

Find the remainder using remainder theorem, when

2x3 – 4x2 + 7x + 6 is divided by x – 2


Answer:

2x3 – 4x2 + 7x + 6 is divided by x – 2


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 2x3 – 4x2 + 7x + 6 and we have (x – 2)


The zero of (x – 2) is 2


Now using Remainder theorem,


p(x) = 2x3 – 4x2 + 7x + 6 is divided by x – 2 then, p(2) is the remainder


p(2) = 2(2)3 – 4(2)2 + 7(2) + 6


= 16 – 16 + 14 +6


= 20


Remainder = 20



Question 4.

Find the remainder using remainder theorem, when

4x3 – 3x2 + 2x – 4 is divided by x + 3


Answer:

4x3 – 3x2 + 2x – 4 is divided by x + 3


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 4x3 – 3x2 + 2x – 4 and we have (x + 3)


The zero of (x + 3) is – 3


Now using Remainder theorem,


p(x) = 4x3 – 3x2 + 2x – 4 is divided by x + 3 then, p(– 3) is the remainder


p(– 3) = 4(–3)3 – 3(–3)2 + 2(–3) – 4


= – 108 – 27 – 6 – 4


= – 145


Remainder = –145



Question 5.

Find the remainder using remainder theorem, when

4x3 – 12x2 + 11x – 5 is divided by 2x – 1


Answer:

4x3 – 12x2 + 11x – 5 is divided by 2x – 1


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 4x3 – 12x2 + 11x – 5 and we have (2x – 1)


The zero of (2x – 1) is


Now using Remainder theorem,


p(x) = 4x3 – 12x2 + 11x – 5 is divided by 2x – 1 then, is the remainder









Remainder = –2



Question 6.

Find the remainder using remainder theorem, when

8x4 + 12x3 – 2x2 – 18x + 14 is divided by x + 1


Answer:

8x4 + 12x3 – 2x2 – 18x + 14 is divided by x + 1


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 8x4 + 12x3 – 2x2 – 18x + 14 and we have (x + 1)


The zero of (x + 1) is – 1


Now using Remainder theorem,


p(x) = 8x4 + 12x3 – 2x2 – 18x + 14 is divided by x + 1 then, p(– 1) is the remainder


p(– 1) = 8(–1)4 + 12(–1)3 – 2(–1)2 – 18(–1) + 14


= 8 – 12 – 2 +18 + 14


= 26


Remainder = 26



Question 7.

Find the remainder using remainder theorem, when

x3 – ax2 – 5x + 2a is divided by x – a


Answer:

x3 – ax2 – 5x + 2a is divided by x – a


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = x3 – ax2 – 5x + 2a and we have (x – a)


The zero of (x – a) is a


Now using Remainder theorem,


p(x) = x3 – ax2 – 5x + 2a is divided by x – a then, p(a) is the remainder


p(a) = (a)3 – a(a)2 – 5(a) + 2a


= a3 – a3 – 5a+ 2a


= – 3a


Remainder = –3a



Question 8.

When the polynomial 2x3 – 2x2 + 9x – 8 is divided by x – 3 the remainder is 28. Find the value of a.


Answer:

2x3 – ax2 + 9x – 8 is divided by x – 3 and remainder = 28


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = 2x3 – ax2 + 9x – 8 and we have (x – 3)


The zero of (x – 3) is 3


Now using Remainder theorem,


p(x) = 2x3 – ax2 + 9x – 8 is divided by x – a then, p(3) is the remainder which is 28


p(3) = 2x3 – ax2 + 9x – 8 =28


= 2(3)3 – a(3)2 + 9(3) – 8 =28


= 54 – 9a + 27 – 8 = 28


= 73 – 9a = 28


= 9a = 73 –28


= 9a = 45



a = 5



Question 9.

Find the value of m if x3 – 6x2 + mx + 60 leaves the remainder 2 when divided by (x + 2).


Answer:

x3 – 6x2 + mx + 60 divided by (x + 2) and remainder = 2


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) = x3 – 6x2 + mx + 60 and we have (x + 2)


The zero of (x + 2) is –2


Now using Remainder theorem,


p(x) = x3 – 6x2 + mx + 60 is divided by x + 2 then, p(–2) is the remainder which is 2


p(–2) = x3 – 6x2 + mx + 60 = 2


= (–2)3 – 6(–2)2 + m(–2) + 60 =2


= – 8 – 24 – 2m + 60 = 2


= – 32 – 2m + 60 = 2


= 28 – 2m = 2


= 2m = 28 – 2


= 2m = 26


m = 13



Question 10.

If (x – 1) divides mx3 – 2x2 + 25x – 26 without remainder find the value of m


Answer:

mx3 – 2x2 + 25x – 26 is divided by (x – 1) without remainder that means remainder = 0


Remainder theorem states that if p(x) is any polynomial and a is any real number and If p(x) is divided by the linear polynomial (x – a) , then the remainder is p(a).


Let p(x) mx3 – 2x2 + 25x – 26 and we have (x – 1)


The zero of (x – 1) is 1


Now using Remainder theorem,


p(x) = mx3 – 2x2 + 25x – 26 is divided by x – 1 then, p(1) is the remainder which is 0


p(1) = mx3 – 2x2 + 25x – 26 = 0


= m(1)3 – 2(1)2 + 25(1) – 26 = 0


= m – 2 + 25 – 26 = 0


= m – 3 = 0


m = 3



Question 11.

If the polynomials x3 + 3x2 – m and 2x3 – mx + 9 leaves the same remainder when they are divided by (x – 2), find the value of m. Also find the remainder


Answer:

x3 + 3x2 – m and 2x3 – mx + 9 is divided by (x – 2) and the remainder is same.


Now let p(x) = x3 + 3x2 – m is divided by x – 2 then, p(2) is the remainder


p(2) = (2)3 + 3(2)2 – m


= 8 + 12 – m


= 20 – m


Now let q(x) = 2x3 – mx + 9 is divided by x – 2 then, q(2) is the remainder


q(2) = 2(2)3 – m(2) + 9


= 16 – 2m + 9


= 25 – 2m


Now, as the question says that the remainder for p(x) and q(x) is same


Therefore, p(2) = q(2)


20 – m = 25 – 2m


2m – m = 25 – 20


m = 5


Remainder = p(2) = 20 – m


= 15




Exercise 3.5
Question 1.

Determine whether (x + 1) is a factor of the following polynomials:

6x4 + 7x3 – 5x – 4


Answer:

Let f(x) = 6x4 + 7x3 – 5x – 4


By factor theorem,


x + 1 = 0 ;x = – 1


If f(– 1) = 0 then (x + 1) is a factor of f(x)


∴f(– 1) = 6(– 1)4 + 7(– 1)3 – 5(– 1) – 4


= 6 – 7 + 5 – 4 = 11 – 11 = 0


∴(x + 1) is a factor of f(x) = 6x4 + 7x3 – 5x – 4



Question 2.

Determine whether (x + 1) is a factor of the following polynomials:

2x4 + 9x3 + 2x2 + 10x + 15


Answer:

Let f(x) = 2x4 + 9x3 + 2x2 + 10x + 15


By factor theorem,


x + 1 = 0 ;x = – 1


If f(– 1) = 0 then (x + 1) is a factor of f(x)


∴f(– 1) = 2(– 1)4 + 9(– 1)3 + 2(– 1)2 + 10(– 1) + 15


= 2 – 9 + 2 – 10 + 15 = 19 – 19 = 0


∴(x + 1) is a factor of f(x) = 2x4 + 9x3 + 2x2 + 10x + 15



Question 3.

Determine whether (x + 1) is a factor of the following polynomials:

3x3 + 8x2 + 6x – 5


Answer:

Let f(x) = 3x3 + 8x2 + 6x – 5


By factor theorem,


x + 1 = 0 ;x = – 1


If f(– 1) = 0 then (x + 1) is a factor of f(x)


∴f(– 1) = 3(– 1)3 + 8(– 1)2 – 6(– 1) – 5


= – 3 + 8 + 6 – 5 = 6(not equal to 0)


∴(x + 1) is not a factor of f(x) = 3x3 + 8x2 + 6x – 5



Question 4.

Determine whether (x + 1) is a factor of the following polynomials:

x3 – 14x2 + 3x + 12


Answer:

Let f(x) = x3 – 14x2 + 3x + 12


By factor theorem,


x + 1 = 0 ;x = – 1


If f(– 1) = 0 then (x + 1) is a factor of f(x)


∴f(– 1) = (– 1)3 – 14(– 1)2 + 3(– 1) + 12


= – 1 – 14 – 3 + 12 = – 6(not equal to 0)


∴(x + 1) is not a factor of f(x) = x3 – 14x2 + 3x + 12



Question 5.

Determine whether (x + 4) is a factor of x3 + 3x2 – 5x + 36.


Answer:

Let f(x) = x3 + 3x2 – 5x + 36.

By factor theorem,


x + 4 = 0: x = – 4


If f(– 4) = 0, then (x + 4) is a factor


∴f(– 4) = (– 4)3 + 3(– 4)2 – 5(– 4) + 36


= – 64 + 48 + 20 + 36


= – 64 + 104 = 40


∴f(– 4) is not equal to 0


So, (x + 4) is not a factor of f(x).



Question 6.

Using factor theorem show that (x – 1) is a factor of 4x3 – 6x2 + 9x – 7.


Answer:

f(x) = 4x3 – 6x2 + 9x – 7

By factor theorem,


(x – 1) = 0 ; x = 1


Since, (x – 1) is a factor of f(x)


Therefore, f(1) = 0


f(1) = 4(1)3 – 6(1)2 + 9(1) – 7 = 4 – 6 + 9 – 7 = 13 – 13 = 0


∴(x – 1) is a factor of f(x)



Question 7.

Determine whether (2x + 1) is a factor of 4x3 + 4x2 – x – 1.


Answer:

Let f(x) = 4x3 + 4x2 – x – 1

By factor Theorem,


2x + 1 = 0 ; x = – 1/2


∴f(– 1/2) = 4(– 1/2)3 + 4(– 1/2)2 – (– 1/2) – 1


= 4(– 1/8) + 4(1/4) + (1/2) – 1


= (– 1/2) + 1 + (1/2) – 1 = 0


∴f(– 1/2) = 0


So, (2x + 1) is a factor of f(x).



Question 8.

Determine the value of p if (x + 3) is a factor of x3 – 3x2 – px + 24.


Answer:

Let f(x) = x3 + 3x2 – px + 24.

By factor theorem,


x + 3 = 0;x = – 3


∴(x + 3) is a factor of f(x)


So, f(– 3) = 0.


f(– 3) = (– 3)3 – 3(– 3)2 – p(– 3) + 24 = 0


= >27 – 27 + 3p + 24 = 0


= > – 59 + 24 + 3p = 0


∴3p – 30 = 0


⇒ p = 30/3


p = 10




Exercise 3.6
Question 1.

The coefficient of x2 & x in 2x3 – 3x2 – 2x + 3 are respectively:
A. 2, 3

B. – 3, – 2

C. – 2, – 3

D. 2, – 3


Answer:


2x3 – 3x2 – 2x + 3: Coefficient of x2 = – 3

Coefficient of x = – 2


Question 2.

The degree of polynomial 4x2 – 7x3 + 6x + 1 is:
A. 2

B. 1

C. 3

D. 0


Answer:

Degree of polynomial = Highest power of x in the polynomial = 3


Question 3.

The polynomial 3x – 2 is a :
A. Linear polynomial

B. Quadratic polynomial

C. Cubic polynomial

D. constant polynomial


Answer:

Given polynomial has degree = 1


Question 4.

The polynomial 4x2 + 2x – 2 is a :
A. Linear polynomial

B. Quadratic polynomial

C. Cubic polynomial

D. constant polynomial


Answer:

Given polynomial has degree = 2


Question 5.

The zero of the polynomial 2x – 5:
A. 5/2

B. – 5/2

C. 2/5

D. – 2/5


Answer:

Given : 2x – 5 = 0


∴ x = 5/2


So, zero of polynomial = 5/2


Question 6.

The root of polynomial equation 3x – 1 is:
A. – 1/3

B. 1/3

C. 1

D. 3


Answer:

Given polynomial equation: 3x – 1 = 0


∴ x = 1/3


So, root = 1/3


Question 7.

The root of polynomial equation x2 + 2x = 0:
A. 0, 2

B. 1, 2

C. 1, – 2

D. 0, – 2


Answer:

Given polynomial equation :


x2 + 2x = 0


∴x(x + 2) = 0


x = 0, x + 2 = 0


x = 0, x = – 2


So, the roots are 0 and – 2


Question 8.

If a polynomial p(x) is divided by (ax + b), then the remainder is:
A. p(b/a)

B. p(– b/a)

C. p(a/b)

D. p(– a/b)


Answer:

f(x) = ax + b


Therefore, by Remainder Theorem, f(x) = 0


ax + b = 0


x = – b/a ∴Remainder = p(x) = p(– b/a)


Question 9.

If a polynomial x3 – ax2 + ax – a is divided by (x – a), then the remainder is:
A. a3

B. a2

C. a

D. – a


Answer:

Given f(x) = x3 – ax2 + ax – 2


By Remainder Theorem,


x – a = 0


x = a


∴Remainder = f(a) = a3 – a3 + 2a – a = a


Question 10.

If (ax – b) is a factor of p(x) then,
A. p(b) = 0

B. p(– b/a) = 0

C. p(a) = 0

D. p(b/a) = 0


Answer:

As (ax – b) is a factor of p(x)


ax – b = 0


∴x = b/a So, p(x) = 0 ;


p(b/a) = 0


Question 11.

One of the factor of x2 – 3x – 10 is :
A. x – 2

B. x + 5

C. x – 5

D. x – 3


Answer:

x2 – 3x – 10 = 0


x2 – 5x + 2x – 10 = 0


x(x – 5) + 2(x – 5) = 0


(x – 5)(x + 2) = 0 Hence, (x – 5) is a factor.


Question 12.

One of the factor of x3 – 2x2 + 2x – 1 is :
A. x – 1

B. x + 1

C. x – 2

D. x + 2


Answer:

Given: f(x) = x3 – 2x2 + 2x – 1 = 0


By hit and trial method,


put x = 1


f(1) = 1 – 2 + 2 – 1 = 0


∴(x – 1) is a factor.