Let us factorise the following polynomials:
x3 – 3x +2
Given, f(x)= x3 – 3x +2
In f(x) putting x=±1, ±2, ±3, we see for which value of x, f(x)=0
f(1)=(1)3−3.(1)+2=0
We observe that f(1) = 0
From factor theorem, we can say, (x−1) is a factor of f(x)
x3 – 3x +2 = x3 – x2 + x2 − x − 2x +2
= x2(x−1)+x(x−1)−2(x−1)
= (x−1)(x2+x−2)
= (x−1)(x2+2x−x−2)
= (x−1)( x(x+2) – (x+2) )
= (x−1)(x−1)(x+2)
= (x−1)2(x+2)
Let us factorise the following polynomials:
x3 + 2x + 3
Given, f(x)= x3 + 2x + 3
In f(x) putting x=±1, ±2, ±3, we see for which value of x, f(x)=0
Since, each term of f(x) is positive here; so for positive value of x we shall not get the value of f(x) as zero.
Hence, for the negative value of x, the value of f(x) can be zero.
f(−1)=(−1)3+2.(−1)+3=0
We observe that f(−1) = 0
From factor theorem, we can say, (x+1) is a factor of f(x)
x3 + 2x + 3 = x3 + x2 – x2 – x + 3x + 3
= x2(x+1)−x(x+1)+3(x+1)
= (x+1)(x2−x+3)
Let us factorise the following polynomials:
a3 – 12a – 16
Given, f(a) = a3 – 12a – 16
In f(a) putting a=±1, ±2, ±3, we see for which value of a, f(a)=0
f(−2)=(−2)3−12.(−2)−16=0
We observe that f(−2) = 0
From factor theorem, we can say, (a+2) is a factor of f(a)
a3 – 12a – 16 = a3 – 12a – 16
= a3+2a2–2a2– 4a – 8a − 16
= a2(a+2)−2a(a+2)−8(a+2)
= (a+2)(a2−2a−8)
= (a+2)(a2−4a+2a−8)
= (a+2)( a(a−4) + 2(a−4) )
= (a+2)(a−4)(a+2)
= (a+2)2(a−4)
Let us factorise the following polynomials:
x3 – 6x + 4
Given, f(x) = x3 – 6x + 4
In f(x) putting x=±1, ±2, ±3, we see for which value of x, f(x)=0
f(2)=(2)3−6.2+4=0
We observe that f(2) = 0
From factor theorem, we can say, (x−2) is a factor of f(x)
x3 – 6x + 4 = x3 – 6x + 4
= x3 −2x2 +2x2 −4x −2x +4
= x2(x−2)+2x(x−2)−2(x−2)
= (x−2)(x2+2x−2)
Let us factorise the following polynomials:
x3 – 19x – 30
Given, f(x)= x3 – 19x – 30
In f(x) putting x=±1, ±2, ±3, we see for which value of x, f(x)=0
f(−2)=(−2)3−19.(−2)+30=0
We observe that f(−2) = 0
From factor theorem, we can say, (x+2) is a factor of f(x)
x3 – 19x – 30 = x3 – 19x – 30
= x3+2x2−2x2−4x−15x −30
= x2(x+2)−2x(x+2)−15(x+2)
= (x+2)(x2−2x−15)
= (x+2)(x2−5x+3x−15)
= (x+2)( x(x−5) + 3(x−5) )
= (x+2)(x−5)(x+3)
Let us factorise the following polynomials:
4a3 – 9a2 + 3a + 2
Given, f(a) = 4a3 – 9a2 + 3a + 2
In f(a) putting a=±1, ±2, ±3, we see for which value of a, f(a)=0
f(1)=4.(1)3 −9.(1)2 +3.(1)+2=0
We observe that f(1) = 0
From factor theorem, we can say, (a−1) is a factor of f(a)
4a3–9a2+3a+2= 4a3−4a2−5a2+5a−2a+ 2
= 4a2(a−1)−5a(a−1)−2(a−1)
= (a−1)(4a2−5a−2)
Let us factorise the following polynomials:
x3 – 9x2 + 23x – 15
Given, f(x)= x3 – 9x2 + 23x – 15
In f(x) putting x=±1, ±2, ±3, we see for which value of x, f(x)=0
f(1)=4.(1)3 −9.(1)2 +3.(1)+2=0
We observe that f(1) = 0
From factor theorem, we can say, (x−1) is a factor of f(x)
x3 – 9x2 + 23x – 15= x3 – 9x2 + 23x – 15
= x3−x2−8x2+8x+15x−15
= x2(x−1)−8x(x−1)+15(x−1)
= (x−1)(x2−8x+15)
= (x−1)(x2−5x−3x+15)
= (x−1)( x(x−5) −3(x−5) )
= (x−1)(x−5)(x−3)
Let us factorise the following polynomials:
5a3 + 11a2 + 4a –2
Given, f(a)= 5a3 + 11a2 + 4a –2
In f(a) putting a=±1, ±2, ±3, we see for which value of a, f(a)=0
f(−1)=5.(−1)3+11.(−1)2+4.(−1)−2=0
We observe that f(−1) = 0
From factor theorem, we can say, (a+1) is a factor of f(a)
5a3 + 11a2 + 4a –2 = 5a3 + 11a2 + 4a –2
= 5a3+5a2+6a2+6a−2a−2
= 5a2(a+1)+6a(a+1)−2(a+1)
= (a+1)(5a2+6a−2)
Let us factorise the following polynomials:
2x3 – x2 + 9x + 5
Given, f(x)= 2x3 – x2 + 9x + 5
In f(x) putting x=±1, , ±2, ±3, we see for which value of x, f(x)=0
f(−)=2.(− )3−(−)2−9.(− )+5=0
We observe that f(−) = 0
From factor theorem, we can say, for (x=−), (2x+1) is a factor of f(x)
2x3 – x2 + 9x + 5 = 2x3 – x2 + 9x + 5
= 2x3+x2−2x2− x + 10x +5
= x2(2x+1)−x(2x+1)+5(2x+1)
= (2x+1)(x2−x+5)
Let us factorise the following polynomials:
2y3 – 5y2 –19y+ 42
Given, f(y)= 2y3 – 5y2 –19y+ 42
In f(y) putting y=±1, ±2, ±3, we see for which value of y, f(y)=0
f(2)=2.(2)3−5.(2)2−19.2+42=0
We observe that f(2) = 0
From factor theorem, we can say, (y−2) is a factor of f(y)
2y3 – 5y2 –19y+ 42= 2y3 – 5y2 –19y+ 42
= 2y3−4y2−y2+2y−21y+42
= 2y2(y−2)−y(y−2)−21(y−2)
= (y−2)(2y2−y−21)
Given,
⇒ This can be written as
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
Let us factorise the following algebraic expressions:
Given, m2 + + 2 – 2m –
Let us factorise the following algebraic expressions:
9p2 – 24pq + 16q2 + 3ap – 4aq
Given, 9p2 – 24pq + 16q2 + 3ap – 4aq
⇒ (3p)2 – 24pq + (4q)2 + 3ap – 4aq
⇒ (3p)2 – 2(3p)(4q) + (4q)2 + 3ap – 4aq
[from Identity I, (x – y)2 = x2 – 2xy + y2]
⇒ (3p – 4q)2 + a(3p – 4q)
⇒ (3p – 4q)[(3p – 4q) + a]
⇒ (3p – 4q)(a + (3p – 4q))
Let us factorise the following algebraic expressions:
4x4 + 81
Given, 4x4 + 81
⇒ 4x4 + 34
⇒ (2x2)2 + 92
⇒ (2x2 + 9)2 – 2(2x2)(9)
⇒ (2x2 + 9)2 – 36x2
⇒ (2x2 + 9)2 – (6x)2
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ ((2x2 + 9) – (6x)) ((2x2 + 9) + (6x))
⇒ (2x2 + 9 – 6x)(2x2 + 9 + 6x)
Let us factorise the following algebraic expressions:
x4 – 7x2 + 1
Given, x4 – 7x2 + 1
Can be written as
⇒ (x2 + 1)2 – 9x2
⇒ (x2 + 1)2 – (3x)2
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ ((x2 + 1) – 3x)((x2 + 1) + 3x)
⇒ (x2 – 3x + 1)(x2 + 3x + 1)
Let us factorise the following algebraic expressions:
p4 – 11p2q2 + q4
Given, p4 – 11p2q2 + q4
⇒ (p2)2 – 11p2q2 + (q2)2
⇒ (p2)2 – 2p2q2 – 9 p2q2 + (q2)2
⇒ (p2)2 – 2p2q2 + (q2)2 – 9 p2q2
⇒ (p2 – q2)2 – (3pq)2
⇒ ((p2 – q2) – 3pq)((p2 – q2) + 3pq)
⇒ (p2 – q2 – 3pq)(p2 – q2 + 3pq)
Let us factorise the following algebraic expressions:
a2 + b2 – c2 – 2ab
Given, a2 + b2 – c2 – 2ab
⇒ This can be written as a2 – 2ab + b2 – c2
⇒ From the identity II, a2 – 2ab + b2 = (a – b)2
∴ (a – b)2 – c2
⇒ ((a – b) – c)((a – b) + c)
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ (a – b – c)(a – b + c)
Let us factorise the following algebraic expressions:
3a (3a + 2c) – 4b (b + c)
Given, 3a(3a + 2c) – 4b(b + c)
⇒ 9a2 + 6ac – 4b2 – 4bc
⇒ (3a)2 + 2(3)(ac) – (2b)2 – 4bc + c2 – c2
⇒ (3a)2 + 2(3)(ac) + c2 – ((2b)2 + 2(2b)(c) + c2)
⇒ (3a + c)2 – (2b + c)2
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ (3a + c – 2b – c)(3a + c + 2b + c)
⇒ (3a – 2b)(3a + 2b + 2c)
Let us factorise the following algebraic expressions:
a2 – 6ab + 12bc – 4c2
Given, a2 – 6ab + 12bc – 4c2
⇒ a2 – 4c2 – 6ab + 12bc
⇒ (a2 – (2c)2) – 6b(a – 2c)
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ (a + 2c)(a – 2c) – 6b(a – 2c)
⇒ (a – 2c)(a + 2c – 6b)
3a2 + 4ab + b2 – 2ac – c2
Given,3a2 + 4ab + b2 – 2ac – c2
⇒ 3a2 + 4ab + b2 – 2ac – c2
⇒ 4a2 + 4ab + b2 – a2 – 2ac – c2
⇒ From the identity I, a2 + 2ab + b2 = (a + b)2
⇒ 4a2 + 4ab + b2 – (a2 + 2ac + c2)
⇒ (2a + b)2 – (a + c)2
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ ((2a + b) – (a + c))
((2a + b) + (a + c)
⇒ (2a + b – a – c)(2a + b + a + c)
Let us factorise the following algebraic expressions:
x2 – y2 – 6ax + 2ay + 8a2
Given,x2 – y2 – 2(3ax) + 2ay + 9a2 – a2
⇒ x2 – 2(3a)(x) + (3a)2 – (a2 – 2ay + y2)
⇒ (x – 3a)2 – (a – y)2
⇒ (x – 3a – a + y)(x – 3a + a – y)
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ (x – 4a + y)(x – 2a – y)
Let us factorise the following algebraic expressions:
a2 – 9b2 + 4c2 – 25d2 – 4ac + 30bd
Given, a2 – 9b2 + 4c2 – 25d2 – 4ac + 30bd
⇒ a2 – 9b2 + 4c2 – 25d2 – 4ac + 30bd
⇒ a2 – 4ac + 4c2 – 9b2 – 25d2 + 30bd
⇒ a2 – 2(2ac) + (2c)2 – (3b)2 – (5d)2 + 2(3b)(5d)
⇒ (a – 2c)2 – (3b – 5d)2
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ ((a – 2c) – (3b – 5d))(a – 2c – 3b + 5d)
⇒ (a – 2c – 3b – 5d)(a – 2c – 3b + 5d)
Let us factorise the following algebraic expressions:
3a2 – b2 – c2 + 2ab – 2bc + 2ca
Given, 3a2 – b2 – c2 + 2ab – 2bc + 2ca
⇒ 4a2 – a2 – b2 – c2 + 2ab – 2bc + 2ca
⇒ (2a)2 – (a2 + b2 + c2 – 2ab + 2bc – 2ca)
⇒ (2a)2 – (a – b – c)2
[Since, from the identity III we know that, (x2 – y2) = (x – y)(x + y)]
⇒ (2a – (a – b – c))(2a + a + b + c)
⇒ (a + b + c)(3a + b + c)
Let us factorise the following algebraic expressions:
x2 – 2x – 22499
Given, x2 – 2x – 22499
⇒ x2 – 151x + 149x – 22499
⇒ x(x – 151) + 149(x – 151)
⇒ (x + 149)(x – 151)
Let us factorise the following algebraic expressions:
(x2 – y2) (a2 – b2) + 4abxy
Given, (x2 – y2)(a2 – b2) + 4abxy
⇒ ((x – y)(x + y)(a – b)(a + b)) + 4abxy
⇒ (ax)2 – (bx)2 – (ay)2 + (by)2 + 4abxy
⇒ (ax)2 + (by)2 + 4abxy – (bx)2 – (ay)2
⇒ (ax)2 + (by)2 + 2abxy + 2abxy – (bx)2 – (ay)2
[from Identity I, (x + y)2 = x2 + 2xy + y2 and from identity II, (x – y)2 = x2 – 2xy + y2]
⇒ (ax + by)2 – (ay – bx)2
⇒ ((ax + by) + (ay – bx))((ax + by) – (ay – bx))
Let us factorize the following algebraic expressions:
t9 – 512
We know, a3 – b3 = (a – b)(a2 + ab + b2)
Given,
t9 – 512
= (t3)3 – (8)3
= (t3 – 8) (t6 + 8t3 + 64)
= [(t)3 – (2)3] (t6 + 8t3 + 64)
= (t – 2) (t2 + 2t + 4) (t6 + 8t3 + 64)
Let us factorize the following algebraic expressions:
729p6 – q6
We know, a2 – b2 = (a + b) (a – b)
Given,
729p6 – q6
= (27p3)2 – (q3)2
= (27p3 + q3) (27p3 – q3)
Now, a3 – b3 = (a – b)(a2 + ab + b2) and a3 + b3 = (a + b)(a2 – ab + b2)
= [(3p)3 + (q)3] [(3p)3 – (q)3]
= (3p + q)(3p2 – 3pq + q2) (3p – q)(3p2 + 3pq + q2)
Let us factorize the following algebraic expressions:
8(p – 3)3 + 343
We know, a3 – b3 = (a – b)(a2 + ab + b2)
Given,
8(p – 3)3 + 343
= [8(p – 3)]3 + (7)3
= [8(p – 3) + 7] [{8(p – 3)}2 – 8(p – 3).7 + 72]
= (8p – 24 + 7) [64(p – 3)2 – 56(p – 3) + 49]
= (8p – 17) [64(p2 – 6p + 9) – 56p + 168 + 49]
= (8p – 17) [64p2 – 384p + 576 – 56p + 168 + 49]
= (8p – 17) [64p2 – 440p + 793]
Let us factorize the following algebraic expressions:
We know, a3 + b3 = (a + b)(a2 – ab + b2)
Given,
Let us factorize the following algebraic expressions:
(2a3 – b3)3 – b9
Given,
(2a3 – b3)3 – b9
We know, (x – y)3 = x3 – y3 – 3xy(x – y)
Therefore,
= (2a3)3 – (b3)3 – 3(2a3)(b3)(2a3 – b3) – b9
= 8a9 – b9 – 6a3b3(2a3 – b3) – b9
= 8a9 – 12a6b3 + 6a3b6 – 2b9
= 2a9 – 2b9 + 6a9 – 12a6b3 + 6a3b6
= 2(a9 – b9) + 6a3(a6 – 2a3b3 + b6)
Now, we know: x3 – y3 = (x – y)(x2 + xy + y2) and
(x – y)2 = x2 – 2xy + y2
= 2(a3 – b3)(a6 + a3b3 + b3) + 6a3(a3 – b3)2
= 2(a – b)(a2 + ab + b2)(a6 + a3b3 + b6) + 6a3(a – b)2(a2 + ab + b2)2
= 2(a – b)(a2 + ab + b2)(a6 + a3b3 + b6 + 3a3(a – b)(a2 + ab + b2))
= 2(a – b)(a2 + ab + b2)( a6 + a3b3 + b6 + 3a3(a3 + a2b + ab2 – a2b – ab2 – b3)
= 2(a – b)(a2 + ab + b2)( a6 + a3b3 + b6 + 3a3(a3 – b3) )
= 2(a – b)(a2 + ab + b2)( a6 + a3b3 + b6 + 3a6 – 3a3b3 )
= 2(a – b)(a2 + ab + b2)(4a6 – 2a3b3 + b6)
Let us factorize the following algebraic expressions:
AR3 – Ar3 + AR2h – Ar2h
Given,
AR3 – Ar3 + AR2h – Ar2h
= A(R3 – r3 + R2h – r2h)
= A[(R3 – r3) + h(R2 – r2)]
We know, a3 – b3 = (a – b)(a2 + ab + b2) and a2 – b2 = (a + b)(a – b)
= A [(R – r) ( R2 + Rr + r2) + h (R + r)(R – r)]
= A(R – r) [R2 + Rr + r2 + h (R + r)]
= A(R – r) [R(R + r) + r2 + h(R + r)]
= A(R – r) (R + r) (R + r2 + h)
Let us factorize the following algebraic expressions:
a3 + 3a2b + 3ab2 + b3 – 8
Given,
a3 + 3a2b + 3ab2 + b3 – 8
= (a + b)3 – (2)3
We know, a3 – b3 = (a – b)(a2 + ab + b2)
= (a + b – 2) [(a + b)2 + 2(a + b) + 22]
We know, (a + b)2 = a2 + 2ab + b2
= (a + b – 2) [a2 + 2ab + b2 + 2a + 2b + 4]
Let us factorize the following algebraic expressions:
32x4 – 500x
32x4 – 500x
= 4x (8x3 – 125)
= 4x [(2x)3 – (5)3]
We know, a3 – b3 = (a – b)(a2 + ab + b2)
= 4x (2x – 5) [(2x)2 + 2x.5 + (5)2]
= 4x (2x – 5) (4x2 + 10x + 25)
Let us factorize the following algebraic expressions:
8a3 – b3 – 4ax + 2bx
Given,
8a3 – b3 – 4ax + 2bx
= (2a)3 – (b)3 – 2x(2a – b)
We know, a3 – b3 = (a – b)(a2 + ab + b2)
= (2a – b) ((2a)2 + 2a.b + (b)2) – 2x(2a – b)
= (2a – b) (4a2 + 2ab + b2) – 2x(2a – b)
= (2a – b) (4a2 + 2ab + b2 – 2x)
Let us factorize the following algebraic expressions:
x3 – 6x2 + 12x – 35
Given,
x3 – 6x2 + 12x – 35
= x3 – 35 – 6x2 + 12x
= x3 – 35 – 6x(x – 2)
Let us factorise the following algebraic expressions:
x3 + y3 – 12xy + 64
x3 + y3 – 12xy + 64
⇒ x3 + y3 + 43 – 12xy
⇒ x3 + y3 + 43 - 3×4xy …Equation (i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
x3 + y3 + 43 - 3×4xy = (x + y + 4) (x2 + y2 + 16 - xy - 4y - 4x)
(x + y + 4) (x2 + y2 + 16 - xy - 4y - 4x)
Let us factorise the following algebraic expressions:
8x3 – y3 + 1 + 6xy
8x3 – y3 + 1 + 6xy
⇒ (2x) 3 + (- y) 3 + 13 + 6xy
⇒ (2x) 3 + (- y) 3 + 13 - 3×(2x)×(- y)×1 …Equation(i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
⇒ (2x) 3 + (- y) 3 + 13 - 3×(2x)×(- y) = (2x – y + 1) ((2x)2 + y2 + 12 + 2xy + y - 2x)
⇒ (2x) 3 + (- y) 3 + 13 - 3×(2x)×(- y) = (2x – y + 1) (4x2 + y2 + 1 + 2xy + y - 2x)
(2x – y + 1) (4x2 + y2 + 1 + 2xy + y - 2x)
Let us factorise the following algebraic expressions:
8a3 – 27b3 – 1 – 18ab
8a3 – 27b3 – 1 – 18ab
⇒ (2a) 3 + (- 3b) 3 + (- 1)3 - 18ab
⇒ (2a) 3 + (- 3b) 3 + (- 1)3 - 3×(2a)×(- 3b)×(- 1) …Equation(i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
⇒ (2a) 3 + (- 3b) 3 + (- 1)3 - 3×(2a)×(- 3b)×(- 1) = (2a - 3b - + 1) (4a2 + 9b2 + 1 + 6ab - 3b - 2a)
(2a - 3b - 1) (4a2 + 9b2 + 1 - 6ab + 3b + 2a)
Let us factorise the following algebraic expressions:
1 + 8x3 + 18xy – 27y3
1 + 8x3 + 18xy – 27y3
⇒ 13 + (2x) 3 + (- 3y) 3 + 18xy
⇒ 13 + (2x) 3 + (- 3y) 3 + 3×(1)×(2x) (- 3y) …Equation(i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
⇒ 13 + (2x) 3 + (- 3y) 3 + 3×(1)×(2x) (- 3y) = (1 + 2x - 3y) (1 + 4x2 + 9y2 - 2x + 6xy + 3y)
(1 + 2x - 3y) (1 + 4x2 + 9y2 - 2x + 6xy + 3y)
Let us factorise the following algebraic expressions:
(3a – 2b)3 + (2b – 5c)3 + (5c – 3a)3
Let us consider (3a - 2b) = x, (2b - 5c) = y, (5c - 3a) = z
So x + y + z = 3a – 2b + 2b – 5c + 5c – 3a = 0
(3a – 2b) 3 + (2b – 5c) 3 + (5c – 3a) 3 = x3 + y3 + z3
Since x + y + z = 0, hence
x3 + y3 + z3 = 3xyz
⇒ (3a – 2b) 3 + (2b – 5c) 3 + (5c – 3a) 3 = 3×(3a – 2b)×(2b – 5c)× (5c – 3a)
3(3a – 2b) (2b – 5c) (5c – 3a)
Let us factorise the following algebraic expressions:
(2x – y)3 – (x + y)3 + (2y – x)3
Let us consider (2x – y) = a, (2y – x) = b
a + b = (2x – y) + (2y – x) = x + y
So we can say that
(2x – y) 3 – (x + y) 3 + (2y – x) 3 = a3 + b3 – (a + b) 3 …Equation (i)
Using the identity of (a + b) 3 we get
(a + b) 3 = a3 + b3 + 3ab(a + b)
⇒ - 3ab(a + b) = a3 + b3 - (a + b)3
Using the above identity in Equation (i)
(2x – y) 3 – (x + y) 3 + (2y – x) 3 = - 3ab(a + b)
⇒ (2x – y) 3 – (x + y) 3 + (2y – x) 3 = - 3×(2x – y)× (2y – x)× (x + y)
⇒ (2x – y) 3 – (x + y) 3 + (2y – x) 3 = 3×(2x – y)× (x - 2y)× (x + y)
3(2x – y) (x - 2y) (x + y)
Let us factorise the following algebraic expressions:
a6 + 32a3 – 64
a6 + 32a3 – 64
⇒ a6 + 8a3 – 64 + 24a3
⇒ (a2)3 + (2a) 3 + (- 4)3 - 3×(a2)×(2a)×(- 4) …Equation (i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
⇒ (a2)3 + (2a) 3 + (- 4)3 - 3×(a2)×(2a)×(- 4) = (a2 + 2a - 4) (a4 + 4a2 + 16 - 2a3 + 8a + 4a2)
⇒ (a2 + 2a - 4) (a4 + 8a2 + 16 - 2a3 + 8a)
(a2 + 2a - 4) (a4 - 2a3 + 8a2 + 8a + 16)
Let us factorise the following algebraic expressions:
a6 – 18a3 + 125
a6 – 18a3 + 125
⇒ a6 + 27a3 + 125 - 45a3
⇒ (a2)3 + (3a) 3 + 53 - 45a3
⇒ (a2)3 + (3a) 3 + 53 – 3× a2× 3a× 5 …Equation (i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
⇒ (a2)3 + (3a) 3 + 53 – 3× a2× 3a× 5 = (a2 + 3a + 5) (a4 + 9a2 + 25 - 3a3 - 15a - 5a2)
⇒ (a2)3 + (3a) 3 + 53 – 3× a2× 3a× 5 = (a2 + 3a + 5) (a4 + 4a2 + 25 - 3a3 - 15a)
(a2 + 3a + 5) (a4 - 3a3 + 4a2 - 15a + 25)
Let us factorise the following algebraic expressions:
p3 (q – r)3 + q3 (r – p)3 + r3 (p – q)3
p3 (q – r) 3 + q3 (r – p) 3 + r3 (p – q) 3
⇒ (pq – pr) 3 + (qr – pq) 3 + (pr – qr) 3
Let us consider pq – pr = a, qr – pq = b, pr – qr = c
a + b + c = pq – pr + qr – pq + pr – qr = 0
Since a + b + c = 0, hence
a3 + b3 + c3 = 3abc
⇒ p3 (q – r) 3 + q3 (r – p) 3 + r3 (p – q) 3 = 3pqr(q - r) (r – p) (p – q)
3pqr (q - r) (r – p) (p – q)
Let us factorise the following algebraic expressions:
…Equation (i)
We use the identity
a3 + b3 + c3 - 3abc = (a + b + c) (a2 + b2 + c2 - ab - bc - ca)
Using the above identity in Equation (i) we get
Let us factorise the following algebraic expressions:
(a + b)2 – 5a – 5b – 6
The given expression can be rewritten as:
(a + b)2 – 5(a + b) + 6
Assume (a + b) = p,
⇒ p2 – 5p+ 6
⇒ p2 – 2p - 3p + 6
⇒ p(p - 2) -3(p - 2)
⇒ (p – 3)(p – 2)
On substituting the value of p, we get,
(a +b - 3)(a + b – 2)
Let us factorise the following algebraic expressions:
(x + 1) (x + 2) (3x – 1) (3x – 4) + 12
The given expression can be rewritten as:
(x + 1)(3x – 1)(x + 2)(3x – 4) + 12
⇒ (3x2 – x + 3x - 1)(3x2 - 4x + 6x - 8) + 12
⇒ (3x2 + 2x - 1)(3x2 + 2x - 8) + 12
Let 3x2 + 2x = p
⇒ (p - 1)( p – 8) + 12
⇒ p2 – 9x + 8 + 12
⇒ p2 – 9p + 20
⇒ p2 – 5p – 4p + 20
⇒(p – 5)(p – 4)
On substituting the value of p, we get,
⇒ (3x2 + 2x – 5)(3x2 + 2x – 4)
⇒(3x2 + 5x – 3x – 5)(3x2 + 2x – 4)
⇒ (x(3x + 5) – 1(3x + 5))(3x2 + 2x – 4)
⇒ (x – 1)(3x + 5) (3x2 + 2x – 4)
Let us factorise the following algebraic expressions:
x(x2 – 1) (x + 2) – 8
As we know that,
a2 – b2 = (a – b)(a + b)
The given expression can be rewritten as:
x(x + 1)(x – 1)(x + 2) – 8
⇒ (x2 + x)(x2 + x – 2) – 8
Let x2 + x = p
⇒ p(p – 2) – 8
⇒ p2 – 2p – 8
⇒ p2 – 4p + 2p – 8
⇒ p(p – 4) + 2(p – 4)
⇒ (p + 2)(p – 4)
On substituting the value of p, we get,
⇒ (x2 + x + 2)(x2 + x – 4)
Let us factorise the following algebraic expressions:
7(a2 + b2)2 – 15(a4 – b4) + 8 (a2 – b2)2
As we know that,
x2 – y2 = (x – y)(x + y)
The given expression can be rewritten as:
7(a2 + b2)2 – 15(a2 + b2)(a2 – b2) + 8 (a2 – b2)2
Let (a2 + b2) = p and (a2 – b2) = q
⇒ 7p2 – 15pq + 8q2
⇒ 7p2 – 7pq – 8pq + 8q2
⇒ 7p(p – q) – 8q(p – q)
⇒ (7p – 8q)(p – q)
On substituting the value of p and q, we get,
⇒ (7(a2 + b2) - 8(a2 – b2))( a2 + b2 – a2 + b2)
⇒ (7a2 + 7b2 – 8a2 + 8b2) (2b2)
⇒ 2b2(15b2 – a2)
Let us factorise the following algebraic expressions:
(x2 – 1)2 + 8x(x2 + 1) + 19x2
As we know that,
a2 – b2 = (a – b)(a + b)
The given expression can be rewritten as:
(x + 1)2(x – 1)2 + 8x(x2 + 1) + 19x2
Using (a – b)2 = a2 + b2 – 2ab, and
(a + b)2 = a2 + b2 + 2ab
⇒ (x2 + 1 + 2x)(x2 + 1 – 2x) + 8x(x2 + 1) + 19x2
Let x2 + 1 =p
⇒ (p + 2x)(p – 2x) + 8xp + 19x2
⇒ p2 – 4x2 + 8xp + 19x2
⇒ p2 + 8xp + 15x2
⇒ p2 + 3xp + 5xp + 15x2
⇒ p(p+3x) + 5x(p + 3x)
⇒ (p + 5x)(p + 3x)
On substituting the value of p, we get,
⇒ (x2 + 5x + 1)(x2 + 3x + 1)
Let us factorise the following algebraic expressions:
(a – 1)x2 – x – (a – 2)
The given expression can be rewritten as:
(a – 1)x2 – x((a - 1) – (a - 2)) – (a – 2)
⇒ (a – 1)x(x – 1) + (a – 2)(x – 1)
⇒ (x – 1)(ax – x + a - 2)
Let us factorise the following algebraic expressions:
(a – 1)x2 + a2xy + (a + 1)y2
Let p = (a – 1) and q = (a+1)
As we know that, a2 – b2 = (a – b)(a + b)
⇒ pq = a2 + 1
The given expression can be rewritten as:
px2 + pqxy + pq + qy2
⇒ px(x + qy) + y(x + qy)
⇒ (px + y)(x + qy)
On substituting the value of p and q, we get,
(ax – x + y)(x + ay + y)
Let us factorise the following algebraic expressions:
x2 – qx – p2 + 5pq – 6q2
The given expression can be rewritten as:
X2 – qx – (p2 – 5pq + 6q2)
⇒ x(x – q) – (p2 – 2pq - 3pq + 6q2)
⇒ x2 – qx – (p – 2q)(p – 3q)
⇒ x2 + (p – 2q)x – (p – 3q)x – (p – 2q)(p – 3q)
⇒ (x – p + 2q)(x + p – 3q)
Let us factorise the following algebraic expressions:
The given expression can be rewritten as:
As we know that, x2 + y2 - 2xy = (x – y)2
Let
⇒ 2p2 – p – 3
⇒ 2p2 – 3p + 2p – 3
⇒ p(2p – 3) + (2p – 3)
⇒ (p + 1) (2p – 3)
On substituting the value of p, we get,
Let us factorise the following algebraic expressions:
(x2 – x) y2 + y – (x2 + x)
The given expression can be rewritten as:
x(x – 1)y2 + x2y – (x2 – 1)y – x(x+1)
⇒ x2 – xy2 + x2y – x2y + y – x2 – x
As we know that a2 – b2 = (a + b)(a – b)
⇒ xy[(x – 1)y + x] – (x + 1)[(x – 1)y + x]
⇒ (xy – x - 1)(xy + x – y)
If a2 – b2 = 11 × 9 and a & b are positive integers (a>b) then
A. a = 11, b =9
B. a = 33, b = 3
C. a = 10, b =1
D. a = 100, b =1
Using the identity x2 – y2 = (x + y)(x – y)
⇒ (a + b)(a – b) = 11 × 9
Since 11 is a prime number therefore the factors can be equated,
⇒ a + b = 11
And a – b = 9
On solving above two equations we get,
a = 10 and b = 1
If then the value of a3 + b3 is
A. 1
B. a
C. b
D. 0
The given equation on LCM reduces to:
a2 + b2 = ab
Also we know that,
a3 + b3 = (a + b)(a2 + b2 – ab)
On substituting the value of a2 + b2 in above equation, we get,
⇒ (a + b) (ab – ab)
⇒ 0
The value of 253 – 753 + 503 + 3 × 25 × 75 × 50 is
A. 150
B. 0
C. 25
D. 50
The given expression can be rewritten as:
253 – 753 – (25 – 75)3 - 3(25)(75)(25 – 75)
As we know that,
(a – b)3 = a3 – b3 - 3ab(a - b)
⇒ a3 – b3 - (a – b)3 - 3ab(a - b) = 0
Since we can easily compare the above equation with the given expression by putting a = 25 and b = 75, the value of given expression is 0.
If a + b + c = 0, then the value of is
A. 0
B. 1
C. -1
D. 3
We know the identity that, if a + b+ c = 0, then,
a3 + b3 + c3 = 3abc
If x2 – px + 12 = (x – 3) (x – a) is an identity, then the values of a and p are respectively.
A. a = 4, p = 7
B. a = 7, p = 4
C. a = 4, p = -7
D. a = -4, p = 7
(x – 3) (x – a) = x2 – (3 + a)x + 3a
⇒ 3a = 12
⇒ a = 4
Also, p = 3 + a
⇒ p = 3 + 4 = 7
Short answer type questions:
Let us write the simplest value of
Let p = (b2 – c2), q = (c2 – a2) and r = (a2 – b2)
Since p + q+ r = 0 and we have an identity that if,
x + y + z = 0, the x3 + y3 + z 3 = 3xyz
⇒ p3 + q3 + r3 = 3pqr
Similarly in denominator of given fraction, we see that sum of all the individual terms is equal to 0, so same identity can be applied in denominator as well.
The fractions reduces to:
Also as, x2 – y2 = (x - y)(x + y)
Short answer type questions:
Let us write the relation of a, b and c if a3 + b3 + c3 – 3abc = 0 and a + b + c ≠ 0.
As we know from the identity that,
a3 + b3 + c3 – 3abc = (a + b + c)(a2 + b2 + c2 – ab – bc – ca)
Since a + b + c ≠ 0, that means,
a2 + b2 + c2 – ab – bc – ca = 0
Multiplying both sides by 2, we get,
a2 + b2 – 2ab + b2 + c2 – 2bc + a2 + c2 – 2ac = 0
⇒ (a – b)2 + (b – c)2 + (a – c)2 = 0
Now this is only possible if:
a – b = 0, b – c = 0 and a – c =0
⇒ a = b = c
Short answer type questions:
If a2 – b2 = 224 and a and b are negative integers (a < b), then let us write the values of a and b.
224 can be written as 16 × 14
224 = (-16) × (-14)
Also using the identity, x2 – y2 = (x + y)(x – y)
⇒ a2 – b2 = (a + b)(a - b) = (-16) × (-14)
On equate the factors, as
a + b = -16 and (a – b) = -14 and solving these two equations, we get,
a = -15 and b = -1
Short answer type questions:
Let us write the value of (x – a)3 + (x – b)3 + (x – c)3 – 3(x – a) (x – b) (x – c) if 3x = a + b + c.
As we know the identity that,
If l + m+ n = 0, then l3 + m3 + n3 – 3mnl = 0
Let p = (x - a), q = (x - b), r = (x – c)
p + q + r = (x – a + x – b + x – c) = 3x – a – b – c
also It is given 3x = a + b + c,
⇒ p + q + r = 0
⇒ p3 + q3 + r3 – 3pqr =0
On substituting the values of p, q and r in above equation, we get,
(x – a)3 + (x – b)3 + (x – c)3 – 3(x – a) (x – b) (x – c) = 0
∴ the required value is 0.
Short answer type questions:
Let us write the values of a and p if 2x2 + px + 6 = (2x– a) (x – 2) is an identity.
(2x– a) (x – 2) = 2x2 – 4x – ax + 2a
⇒ 2x2 –x(a + 4) + 2a
Since the above expression is identical to 2x2 + px + 6, therefore their coefficients can be equated.
⇒ 2a = 6
⇒ a =3
Also, p = -(a + 4) = -7
∴ The values of a and p are 3 and -7 respectively.