Expand the following
(5x + 2y + 3z)2
(5x + 2y + 3z)2
The identity is
(x + y + z)2 = x2 + y2 + z2 + 2xy + 2yz + 2zx
∴ (5x + 2y + 3z)2
= (5x)2 + (2y)2 + (3z)2 + 2(5x)(2y) + 2(2y)(3z) + 2(3z)(5x)
= 25x2 + 4y2 + 9z2 + 20xy + 12yz + 30zx
Expand the following
(2a + 3b – c)2
(2a + 3b – c)2
Here the identity used is
(x + y + z)2 = x2 + y2 + z2 + 2xy + 2yz + 2zx
(2a + 3b – c)2 = (2a)2 + (3b)2 + (– c)2 + 2(2a)(3b) + 2(3b)(– c) + 2(– c)(2a)
= 4a2 + 9b2 + c2 + 12ab – 6bc – 4ca
Expand the following
(x – 2y – 4z)2
(x – 2y – 4z)2
Here the identity used is
(x + y + z) 2 = x2 + y2 + z2 + 2xy + 2yz + 2zx
∴ (x – 2y – 4z) 2
= x2 + (– 2y)2 + (– 4z)2 + 2(x)(– 2y) + 2(– 2y)(– 4z) + 2 (– 4z)(x)
= x2 + 4y2 + 16z2 – 4xy + 16yz – 8yz
Expand the following
(P – 2q + r)2
(P – 2q + r)2
Here we use the identity of
(x + y + z)2 = x2 + y2 + z2 + 2xy + 2yz + 2zx
∴ (p – 2q + r)2
= (p)2 + (– 2q)2 + (r)2 + 2(p)(– 2q) + 2(– 2q)(r) + 2(r)(p)
= p2 + 4q2 + r2 – pq – 4qr + 2rp
Find the expansion of
(x + 1)(x + 4)(x + 7)
(x + 1) (x + 4) (x + 7)
we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (x + 1)(x + 4)(x + 7)
= x3 + (1 + 4 + 7) x2 + (1 × 4 + 4 × 7 + 7 × 1) x + 1 × 4 × 7
= x3 + 12x2 + (4 + 28 + 7) x + 28
= x3 + 12x2 + 39x + 28
Find the expansion of
(p + 2)(p – 4)(p + 6)
(p + 2)(p – 4)(p + 6)
Here the identity used is
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (p + 2)(p – 4)(p + 6)
= p3 + (2 – 4 + 6) p2 + (2(– 4) + (– 4)6 + 6(2))p + (2)(– 4)(6)
= p3 + 4p2 + (– 8 – 24 + 12)p – 48
= p3 + 4p2 – 20p – 48
Find the expansion of
(x + 5)(x – 3)(x – 1)
(x + 5)(x – 3)(x – 1)
Here the identity used is
(x + a)(x + b)(x + c) = x3 + (a + b + c) x2 + (ab + bc + ca)x + abc
∴ (x + 5)(x – 3)(x – 1)
= x3 + (5 – 3 – 1) x2 + (5(– 3) + (– 3)(– 1)(– 1)5)x + 5(– 3)(– 1)
= x3 + x2 + (– 15 + 3 – 5) x + 15
= x3 + x2 – 17x + 15
Find the expansion of
(x – a)(x – 2a)(x – 4a)
(x – a)(x – 2a)(x – 4a)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (x – a)(x – 2a)(x – 4a)
= x3 + (– a – 2a – 3a)x2 + [(– a)(– 2a) + (– 2a)(– 3a) + (– 3a)(– a)]x + (– a)(– 2a)(– 3a)
= x3 – 6ax2 + (2a2 + 6a2 + 3a2)x – 6a3
= x3 – 6ax2 + 11a2x – 6a3
Find the expansion of
(3x + 1)(3x + 2)(3x + 5)
(3x + 1)(3x + 2)((3x + 5)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (3x + 1)(3x + 2)((3x + 5)
= (3x)3 + (1 + 2 + 5)(3x)2 + (1 × 2 + 2 × 5 + 5 × 1)(3x) + 1 × 2 × 5
= 27 x3 + (8)9x2 + (2 + 10 + 5) (3x) + 1 × 2 × 5
= 27 x3 + 72x2 + 51x + 10
Find the expansion of
(2x + 3)(2x – 5)(2x – 7)
(2x + 3)(2x – 5)(2x – 7)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (2x + 3)(2x – 5)(2x – 7)
= (2x)3 + (3 – 5 – 7)(2x)2 + [(3)(– 5) + (– 5)(– 7) + (– 7)(3)](2x) + (3)(– 5)(– 7)
= 8x3 + (– 9)(4x2) + (– 15 + 35 – 21)(2x) + 105
= 8x3 – 36 x2 – 2x + 105
Using algebraic identities find the coefficients of x2 term, x term and constant term.
(x + 7)(x + 3)(x + 9)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (x + 7)(x + 3)(x + 9)
= x3 + (7 + 3 + 9)x2 + (7 × 3 + 3 × 9 + 9 × 7)x + 7 × 3 × 9
= x3 + 19x2 + (21 + 27 + 63)x + 189
= x3 + 19x2 + 111x + 189
Coefficient of
x2 = 19
x = 111
Constant term = 189
Using algebraic identities find the coefficients of x2 term, x term and constant term.
(x – 5)(x – 4)(x + 2)
(x – 5)(x – 4)(x + 2)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ (x – 5)(x – 4)(x + 2)
= x3 + (– 5 – 4 + 2)x2 + {(– 5) × (– 4) + (– 4) × 2 + 2 × (– 5)}x + (– 5)(– 4)2
= x3 – 7x2 + (20 – 8 – 10)x + 40
= x3 – 7x2 + 2x + 40
Coefficient of
x2 = – 7
x = 2 and
Constant term = 40
Using algebraic identities find the coefficients of x2 term, x term and constant term.
(2x + 3)(2x + 5)(2x + 7)
(2x + 3)(2x + 5)(2x + 7)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)(x)2 + (ab + bc + ca)x + abc
∴ (2x + 3) (2x + 5)(2x + 7)
= (2x)3 + 4(3 + 5 + 7)x2 + (15 + 35 + 21)2x + 105
= 8x3 + 60x2 + 142x + 105
Coefficient of
x2 = 60
x = 142
Constant term = 105
Using algebraic identities find the coefficients of x2 term, x term and constant term.
(5x + 2)(1 – 5x)(5x + 3)
(5x + 2)(1 – 5x)(5x + 3)
Here we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
∴ – (5x + 2)(5x – 1)(5x + 3)
here x = 5x, a = 2, b = – 1 and c = 3
= – (5x)3 – (2 – 1 + 3)(5x)2 – (– 2 – 3 + 6)5x + 6
= – 125x3 – 100x2 – 5x + 6
Here coefficient of
x2 = – 100
x = – 5 and
constant term = 6
If (x + a)(x + b)(x + c) ≡ x3 – 10x2 + 45x – 15 find a + b + c, and a2 + b2 + c2.
Here, we have to use the identity
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
Comparing this with
x3 – 10x2 + 45x – 15 = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
⇒ – 10 = a + b + c
Now,
And (ab + bc + ca) = 45
Now (a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)
⇒ (– 10)2 – 2 × 45 = a2 + b2 + c2
⇒ 100 – 90 = a2 + b2 + c2
⇒ a2 + b2 + c2 = 10
Expand :
(i) (3a + 5b)3
(ii) (4x – 3y)3
(iii)
(i) (3a + 5b)3
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(3a + 5b)3
= (3a)3 + 3 (3a)2(5b) + 3(3a)(5b)2 + (5b)3
= 27a3 + 135a2b + 225ab2 + 125b3
(ii) (4x – 3y)3
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(4x – 3y)3
= (4x)3 + 3(4x)2(– 3y) + 3 × 4x (– 3y)2 + (– 3y)3
= 64x3 – 192 x2 + 108y2 – 27y3
(iii)
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
=
=
Evaluate :
(i) 993
(ii) 1013
(iii) 983
(iv) (102)3
(v) (1002)3
(i) (100 – 1)3
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(100 – 1)3
= (100)3 + 3(100)2 (– 1) + 3(100) (– 1)2 + (– 1)3
= 1000000 – 30000 + 300 – 1
= 970299
(ii) 1013
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(101)3 = (100 + 1)3
= 1003 + 3 × 1002 × 1 + 3 × 100 × 12 + 13
= 1000000 + 30000 + 300 + 1
= 1030301
(iii) 983
= (100 – 2)3
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(100 – 2)3
= 1003 + (– 2)3 + 3(100)2(– 2) + 3(100)(– 2)2
= 1000000 – 8 – 60000 + 1200
= 941192
(iv) (102)3
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(100 + 2)3
= 1003 + 3(100)2 (2) + 3(2)2(100) + (2)3
= 1000000 + 60000 + 1200 + 8
= 1061208
(vi) (1002)3
= (1000 + 2)3
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(1000 + 2)3
= 10003 + 3 × 10002(2) + 3 × 1000 × (2)2 + 23
= 1000000000 + 6000000 + 12000 + 8
= 1006012008
Find 8x3 + 27y3 if 2x + 3y = 13 and xy = 6.
Given 2x + 3y = 13
⇒ (2x + 3y)3 = 133
Here the identity used is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(2x + 3y)3 = (2x)3 + 3(2x)23y + 3(2x)(3y)2 + (3y)3
⇒ 8x3 + 36x2y + 54xy2 + 27y3 = 2197
⇒ 8x3 + 27y3 + 18xy(2x + 3y) = 2197
⇒ 8x3 + 27y3 = 2197 – 108 (2x + 3y) (∵ xy = 6 given)
⇒ 8x3 + 27y3 = 2197 – 108 × 13
⇒ 8x3 + 27y3 = 2197 – 1404
⇒ 8x3 + 27y3 = 793
If x – y = – 6 and xy = 4, find the value of x3 – y3
The identity used here is
(a + b)3 = a3 + 3a2b + 3ab2 + b3
∴ (x – y)3 = x3 + 3x2(– y) + 3x(– y)2 + (– y)3
⇒ x3 – 3x2y + 3xy2 – y3
⇒ (x – y)3 = x3 – 3x2y + 3xy2 – y3
⇒ (– 6)3 = x3 – y3 + 3xy(– x + y)
⇒ – 216 + 3 × 4 (– 6) = x3 – y3
⇒ – 216 – 72 = x3 – y3
⇒ – 288 = x3 – y3
If , find the value of .
Here we use the identity of
(a + b)3 = a3 + 3a2b + 3ab2 + b3
∴
⇒
⇒
⇒
If, find the value of .
Here the identity used
(a + b)3 = a3 + 3a2b + 3ab2 + b3
∴
⇒
⇒
⇒
Simplify:
(i) (2x + y + 4z)(4x2 + y2 + 16z2 – 2xy – 4yz – 8zx)
(ii) (x – 3y – 5z)(x2 + 9y2 + 25z2 + 3xy – 15yz + 5zx)
(i) (2x + y + 4z) (4x2 + y2 + 16z2 – 2xy – 4yz – 8zx)
⇒ Here the identity used is
a3 + b3 + c3 – 3abc = (a + b + c) (a2 + b2 + c2 – ab – bc – ac)
Comparing this with given condition
(2x + y + 4z) (4x2 + y2 + 16z2 – 2xy – 4yz – 8zx) = (2x)3 + y3 + (4z)3 – 3 × 2x × y × 4z
⇒ 8x3 + y3 + 64z3 – 24xyz
(ii) (x – 3y – 5z)(x2 + 9y2 + 25z2 + 3xy – 15yx + 5zx)
⇒ Here the identity used is
a3 + b3 + c3 – 3abc = (a + b + c) (a2 + b2 + c2 – ab – bc – ac)
Comparing this with given condition
(x – 3y – 5z)(x2 + 9y2 + 25z2 + 3xy – 15yx + 5zx)
= x3 + (– 3y)3 + (– 5z)3 – 3(x) (– 3y)(– 5z)
= x3 – 27y3 – 125z3 – 45xyz
Evaluate using identities :
(i) 63 – 93 + 33
(ii) 163 – 63 – 103
(i) 63 – 93 + 33
Here the identity used will be
a3 + b3 + c3 – 3abc = (a + b + c) (a2 + b2 + c2 – ab – bc – ac)
∴ 63 – 93 + 33
⇒ (6 + (– 9) + 3)(62 + (– 9)2 + 32 – 6 × – 9 – (– 9)3 – 6 × 3) + 3 × 6 × – 9 × 3
⇒ 0 (36 + 81 + 9 + 54 + 27 – 18) – 486
⇒ – 486
(ii) 163 – 63 – 103
Here the identity used will be
a3 + b3 + c3 – 3abc = (a + b + c) (a2 + b2 + c2 – ab – bc – ac)
∴ 163 – 63 – 103
= (16 – 6 – 10) (162 + (– 6)2 + (– 10)2 – 16 × – 6 – (– 6)(– 10) – (16)(– 10)) + 3(16) (– 6) (– 10)
= 0 (256 + 36 + 100 + 96 – 60 + 160) + 2880
= 2880
Factorize the following expressions:
2a3 – 3a2b + 2a2c
= 2a3 – 3a2b + 2a2c
Highest common factor is a2
Taking a2 common in the term – 3a2b + 2a2c
we get,
= 2a3 + a2(– 3b + 2c)
Taking a2 common in both the terms
we get,
= a2(2a + (– 3b + 2c))
= a2(2a – 3a + 2c)
2a3 – 3a2b + 2a2c = a2(2a – 3a + 2c)
Factorize the following expressions:
16x + 64x2y
= 16x + 64x2y
Highest common factor is 16x
Taking x common in the term 16x + 64x2y
we get,
= x(16 + 64xy)
= x(16 + 16(4)xy)
Taking 16 common in the term (16 + 64xy)
we get,
= 16x(1 + 4xy)
16x + 64x2y = 16x(1 + 4xy)
Factorize the following expressions:
10x3 – 25x4y
= 10x3 – 25x4y
Highest common factor is 5x3
Taking x3common in the term 10x3 – 25x4y
we get,
= x3 (10– 25xy)
= x3 (5(2)– 5(2)xy)
Taking 5 common in both the terms
we get,
= 5x3 (2– 5xy)
10x3 – 25x4y = 5x3 (2– 5xy)
Factorize the following expressions:
xy – xz + ay – az
= xy – xz + ay – az
Taking x common in xy – xz
we get,
= x(y – z) + ay – az
Taking ‘a’ common in ay – az
we get,
= x(y – z) + a(y – z)
Taking (y – z) common in both the terms
we get,
= (y – z)(x + a)
xy – xz + ay – az = (y – z)(x + a)
Factorize the following expressions:
p2 + pq + pr + qr
= p2 + pq + pr + qr
Taking p common in p2 + pq
we get,
= p(p + q) + pr + qr
Taking r common in pr + qr
we get,
= p(p + q) + r(p + q)
Taking (p + q) common in both the terms
we get,
= (p + q)(p + r)
p2 + pq + pr + qr = (p + q)(p + r)
Factorize the following expressions:
x2 + 2x + 1
= x2 + 2x + 1
Method 1
It is of the form a2 + 2ab + b2
Where a = x and b = 1.
Using the identity: (a + b)2 = a2 + 2ab + b2
We get,
⇒ x2 + 2x + 1 = (x + 1)2
Method 2
Here 2x can be elaborated as x + x
we get,
= x2 + x + x + 1
Taking x common in x2 + x
we get,
= x(x + 1) + x + 1
Taking (x + 1) common in both the terms
we get,
= (x + 1)(x + 1)
= (x + 1)2
x2 + 2x + 1 = (x + 1)2
Factorize the following expressions:
9x2 – 24xy + 16y2
= 9x2 – 24xy + 16y2
Given equation can be simplified as,
= (3x)2 – 2(3x)(4y) + (4y)2
It is of the form a2 – 2ab + b2
Where a = 3x and b = 4y
∴ using the identity (a – b)2 = a2 – 2ab + b2
We get,
⇒ 9x2 – 24xy + 16y2 = (3x – 4y)2
9x2 – 24xy + 16y2 = (3x – 4y)2
Factorize the following expressions:
b2 – 4
= b2 – 4
Given equation can be simplified as,
= (b)2 – (2)2
It is of the form (p)2 – (q)2
where p = b and q = 2
∴ using the identity (p)2 – (q)2 = (p + q)(p – q)
We get,
⇒ b2 – 22 = (b + 2)(b – 2)
b2 – 4 = (b + 2)(b – 2)
Factorize the following expressions:
1 – 36x2
= 1 – 36x2
Given equation can be simplified as,
= (1)2 – (6x)2
It is of the form (p)2 – (q)2
Where p = 1 and q = 6x
∴ using the identity: (p)2 – (q)2 = (p + q)(p – q)
We get,
⇒ (1)2 – (6x)2 = (1 + 6x)(1 – 6x)
1 – 36x2 = (1 + 6x)(1 – 6x)
Factorize the following expressions:
p2 + q2 + r2 + 2pq + 2qr + 2rp
Method 1
= p2 + q2 + r2 + 2pq + 2qr + 2rp
= (p)2 + (q)2 + (r)2 + 2(p)(q) + 2(q)(r) + 2(r)(p)
It is of the from a2 + b2 + c2 + 2ab + 2bc + 2ca
where a = p, b = q, c = r
Using the identity (a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca
We get,
⇒ p2 + q2 + r2 + 2pq + 2qr + 2rp = (p + q + r)2
Method 2
= p2 + q2 + r2 + 2pq + 2qr + 2rp
The above equation can be simplified as
= p2 + 2pq + q2 + r2 + 2qr + 2rp
= (p + q)2 + r2 + 2qr + 2rp (∵ a2 + 2ab + b2 = (a + b)2)
Taking 2r common in the term 2qr + 2rp
we get,
= (p + q)2 + r2 + 2r(q + p)
Rearranging the above equation as
= (p + q)2 + 2r(q + p) + r2
This is of the from a2 + 2ab + b2
Where, a = p + q and b = r
Using the identity: (a + b)2 = a2 + 2ab + b2
We get,
⇒ p2 + q2 + r2 + 2pq + 2qr + 2rp = ((p + q) + r)2
= (p + q + r)2
p2 + q2 + r2 + 2pq + 2qr + 2rp = (p + q + r)2
Factorize the following expressions:
a2 + 4b2 + 36 – 4ab + 24b – 12a
= a2 + 4b2 + 36 – 4ab + 24b – 12a
Method 1
The above equation can be simplified as :
= (– a)2 + (2b)2 + (6)2 + 2(– a)(2b) + 2(2b)(6) + 2(– a)(6)
This equation is of the form: p2 + q2 + r2 + 2pq + 2qr + 2rp
where p = – a, q = 2b, r = 6
Using the identity: p2 + q2 + r2 + 2pq + 2qr + 2rp = (p + q + r)2
We get,
⇒ a2 + 4b2 + 36 – 4ab + 24b – 12a = (– a + 2b + 6)2
= (– a + 2b + 6)2
= (– 1)2(a – 2b – 6)2
= (a – 2b – 6)2
Method 2
The above equation can be simplified as
= (– a)2 + (2b)2 + (6)2 + 2(– a)(2b) + 2(2b)(6) + 2(– a)(6)
= {(– a)2 + 2(– a)(2b) + (2b)2} + (6)2 + 2(2b)(6) + 2(– a)(6)
(∵ a2 + 2ab + b2 = (a + b)2)
(– a + 2b)2 + (6)2 + 2(2b)(6) + 2(– a)(6)
Taking 2(6) common in term 2(2b)(6) + 2(– a)(6)
= (– a + 2b)2 + 2(6)(– a + 2b) + (6)2
This of the form: (p + q)2 + 2r(p + q) + r2
Where, p = – a, q = 2b and r =6
Using the identity: (p + q)2 = p2 + 2pq + q2
We get,
⇒ a2 + 4b2 + 36 – 4ab + 24b – 12a = (– a + 2b + 6)2
= (– a + 2b + 6)2
= (– 1)2(a – 2b – 6)2
= (a – 2b – 6)2
a2 + 4b2 + 36 – 4ab + 24b – 12a = (– a + 2b + 6)2
Factorize the following expressions:
9x2 + y2 + 1 – 6xy + 6x – 2y
Method 1
The above equation can be simplified as :
= (3x)2 + (– y)2 + (1)2 + 2(3x)(– y) + 2(3x)(1) + 2(– y)(1)
This equation is of the form: p2 + q2 + r2 + 2pq + 2qr + 2rp
where p =3x, q = – y, r = 1
Using the identity: p2 + q2 + r2 + 2pq + 2qr + 2rp = (p + q + r)2
We get,
⇒ 9x2 + y2 + 1 – 6xy + 6x – 2y = (3x – y + 1)2
= (3x – y + 1)2
Method 2
The above equation can be simplified as:
= (3x)2 + (– y)2 + (1)2 + 2(3x)(– y) + 2(3x)(1) + 2(– y)(1)
= {(3x)2 + 2(3x)(– y) + (– y)2} + (1)2 + 2(3x)(1) + 2(– y)(1)
(∵ p2 + 2pq + q2 = (p + q)2)
= (3x – y)2 + (1)2 + 2(3x)(1) + 2(– y)(1)
Taking 2(1) common in term 2(3x)(1) + 2(– y)(1)
= (3x – y)2 + (1)2 + 2(1)(3x – y)
= (3x – y)2 + 2(1)(3x – y) + (1)2
This of the form: (p + q)2 + 2r(p + q) + r2
Where, p = 3x, q = – y and r = 1
Using the identity: (a + b)2 = a2 + 2ab + b2
We get,
⇒ 9x2 + y2 + 1 – 6xy + 6x – 2y = (3x – y + 1)2
9x2 + y2 + 1 – 6xy + 6x – 2y = (3x – y + 1)2
Factorize the following expressions:
4a2 + b2 + 9c2 – 4ab – 6bc + 12ca
Method 1
The above equation can be simplified as :
= (2a)2 + (– b)2 + (3c)2 + 2(2a)(– b) + 2(– b)(3c) + 2(3c)(2a)
This equation is of the form: p2 + q2 + r2 + 2pq + 2qr + 2rp
where p =2a, q = – b, r = 3c
Using the identity: p2 + q2 + r2 + 2pq + 2qr + 2rp = (p + q + r)2
We get,
⇒ 4a2 + b2 + 9c2 – 4ab – 6bc + 12ca = (2a – b + 3c)2
= (2a – b + 3c)2
Method 2
The above equation can be simplified as:
= (2a)2 + (– b)2 + (3c)2 + 2(2a)(– b) + 2(– b)(3c) + 2(3c)(2a)
= {(2a)2 + 2(2a)(– b) + (– b)2} + (3c)2 + 2(– b)(3c) + 2(3c)(2a)
(∵ p2 + 2pq + q2 = (p + q)2)
= (2a – b)2 + (3c)2 + 2(– b)(3c) + 2(3c)(2a)
Taking 2(3c) common in term 2(– b)(3c) + 2(3c)(2a)
= (2a – b)2 + (3c)2 + 2(3c)(– b + 2a)
= (2a – b)2 + 2(3c)(2a – b) + (3c)2
This of the form: (p + q)2 + 2r(p + q) + r2
Where, p = 2a, q = – b and r = 3c
Using the identity: (p + q)2 = p2 + 2pq + q2
We get,
⇒ 4a2 + b2 + 9c2 – 4ab – 6bc + 12ca = (2a – b + 3c)2
4a2 + b2 + 9c2 – 4ab – 6bc + 12ca = (2a – b + 3c)2
Factorize the following expressions:
25x2 + 4y2 + 9z2 – 20xy + 12yz – 30zx
Method 1
The above equation can be simplified as :
= (– 5x)2 + (2y)2 + (3z)2 + 2(– 5x)(2y) + 2(2y)(3z) + 2(3z)(– 5x)
This equation is of the form: p2 + q2 + r2 + 2pq + 2qr + 2rp
where p = – 5x, q = 2y, r = 3z
Using the identity: p2 + q2 + r2 + 2pq + 2qr + 2rp = (p + q + r)2
We get,
⇒ 25x2 + 4y2 + 9z2 – 20xy + 12yz – 30zx = (– 5x + 2y + 3z)2
= (– 5x + 2y + 3z)2
= (– 1)2(5x – 2y – 3z)2
= (5x – 2y – 3z)2
Method 2
The above equation can be simplified as:
= (– 5x)2 + (2y)2 + (3z)2 + 2(– 5x)(2y) + 2(2y)(3z) + 2(3z)(– 5x)
= {(– 5x)2 + 2(– 5x)(2y) + (2y)2} + (3z)2 + 2(2y)(3z) + 2(3z)(– 5x)
(∵ p2 + 2pq + q2 = (p + q)2)
= (– 5x + 2y)2 + (3z)2 + 2(2y)(3z) + 2(3z)(– 5x)
Taking 2(3z) common in term 2(2y)(3z) + 2(3z)(– 5x)
= (– 5x + 2y)2 + (3z)2 + 2(3z)(2y – 5x)
= (– 5x + 2y)2 + 2(3z)(2y – 5x) + (3z)2
This of the form: (p + q)2 + 2r(p + q) + r2
Where, p = – 5x, q = 2y and r = 3z
Using the identity: (p + q)2 = p2 + 2pq + q2
We get,
⇒ 25x2 + 4y2 + 9z2 – 20xy + 12yz – 30zx = (– 5x + 2y + 3z)2
= (– 5x + 2y + 3z)2
= (– 1)2(5x – 2y – 3z)2
= (5x – 2y – 3z)2
25x2 + 4y2 + 9z2 – 20xy + 12yz – 30zx = (5x – 2y – 3z)2
Factorize the following expressions:
27x3 + 64y3
The above equation can be simplified as
= (3x)3 + (4y)3
Both the given terms are perfect cubes, factor using the sum of cubes formula,
(a)3 + (b)3 = (a + b)(a2 – ab + b2)
Here a = 3x and b = 4y
⇒ (3x)3 + (4y)3 = (3x + 4y)((3x)2 – (3x)(4y) + (4y)2)
= (3x + 4y)(9x2 – 12xy + 16y2)
27x3 + 64y3 = (3x + 4y)(9x2 – 12xy + 16y2)
Factorize the following expressions:
m3 + 8
The above equation can be simplified as
= (m)3 + (2)3
Both the given terms are perfect cubes, factor using the sum of cubes formula,
(a)3 + (b)3 = (a + b)(a2 – ab + b2)
Here a = m and b = 2
⇒ (m)3 + (2)3 = (m + 2)((m)2 – (m)(2) + (2)2)
= (m + 2)(m2 – 2m + 4)
m3 + 8 = (m + 2)(m2 – 2m + 4)
Factorize the following expressions:
a3 + 125
The above equation can be simplified as
= (a)3 + (5)3
Both the given terms are perfect cubes, factor using the sum of cubes formula,
(a)3 + (b)3 = (a + b)(a2 – ab + b2)
Here a = a and b = 5
⇒ (a)3 + (5)3 = (a + 5)((a)2 – (a)(5) + (5)2)
= (a + 5)(a2 – 5a + 25)
a3 + 123 = (a + 5)(a2 – 5a + 25)
Factorize the following expressions:
8x3 – 27y3
The above equation can be simplified as
= (2x)3 – (3y)3
Both the given terms are perfect cubes, factor using the subtraction of cubes formula,
(a)3 – (b)3 = (a – b)(a2 + ab + b2)
Here a = 2x and b = 3y
⇒ (2x)3 – (3y)3 = (2x – 3y)((2x)2 + (2x)(3y) + (3y)2)
= (2x – 3y)(4x2 + 6xy + 9y2)
8x3 – 27y3 = (2x – 3y)(4x2 + 6xy + 9y2)
Factorize the following expressions:
x3 – 8y3
The above equation can be simplified as
= (x)3 – (2y)3
Both the given terms are perfect cubes, factor using the subtraction of cubes formula,
(a)3 – (b)3 = (a – b)(a2 + ab + b2)
Here a = x and b = 2y
⇒ (x)3 – (2y)3 = (x – 2y)((x)2 + (x)(2y) + (2y)2)
= (x – y)(x2 + 2xy + 4y2)
x3 – 8y3 = (x – y)(x2 + 2xy + 4y2)
Solve the following equations by substitution method.
x + 3y = 10; 2x + y = 5
[In substitution method, we have to find value of one variable in terms of the other variable from any one of the two given equations . Then, we will substitute this value in the other equation. By doing this, we will get a equation in one variable which can be solved easily]
x + 3y = 10……(1)
2x + y = 5 …..(2)
From eq(1),
X + 3y = 10
⇒ x = 10 – 3y
Substituting the value of x in eq(2)
2x + y = 5
⇒ 2(10 – 3y) + y = 5
⇒ 20 – 6y + y = 5
⇒ 20 – 5y = 5
⇒ 5y = 20 – 5
⇒ 5y = 15
Substituting value of y in eq(1)
x + 3y = 10
⇒ x + 3×3 = 10
⇒ x + 9 = 10
⇒ x = 10 – 9
⇒ x = 1
Hence,
x = 1, y = 3
Solve the following equations by substitution method.
2x + y = 1; 3x – 4y = 18
[In substitution method, we have to find value of one variable in terms of the other variable from any one of the two given equations . Then, we will substitute this value in the other equation. By doing this, we will get a equation in one variable which can be solved easily]
2x + y = 1….(1)
3x – 4y = 18….(2)
From eq(1),
2x + y = 1….(1)
⇒ y = 1 – 2x
Substituting the value of y in eq(2)
3x – 4y = 18….(2)
⇒ 3x – 4(1 – 2x) = 18
⇒ 3x – 4 + 8x = 18
⇒ 11x + 4 = 18
⇒ 11x = 18 + 4
⇒ 11x = 22
⟹x =
⇒ x = 2
Substituting the value of x in eq(1),
⇒ 2x + y = 1
⇒ 2×2 + y = 1
⇒ y = 1 – 4
⇒ y = – 3
Hence,
x = 2,y = – 3
Solve the following equations by substitution method.
5x + 3y = 21; 2x – y = 4
[In substitution method, we have to find value of one variable in terms of the other variable from any one of the two given equations . Then, we will substitute this value in the other equation. By doing this, we will get a equation in one variable which can be solved easily]
5x + 3y = 21……(1)
2x – y = 4…….(2)
From eq(2)
2x – y = 4
⟹y = 2x – 4…..(3)
Substituting value of y in eq(1)
5x + 3y = 21
⇒ 5x + 3(2x – 4) = 21
⇒ 5x + 6x – 12 = 21
⇒ 11x = 33
⇒ x =
⇒ x = 3
From eq(3)
y = 2x – 4
⇒ y = 2×3 – 4
⇒ y = 2
Hence,
x = 3, y = 2
Solve the following equations by substitution method.
In such questions, if we start question directly, then it will involve LCM of x and y, and a term of xy, which will be inconvenient for us. So, we will assume 1/x as “u “and 1/y as v”]
Let
= u
= v
Then,
= 9
⇒ u + 2v = 9……(1)
And
= 12
⇒ 2u + v = 12……(2)
From eq(1)
u + 2v = 9
⇒ u = 9 – 2v……(3)
Substituting value of u in eq(2)
2u + v = 12
⇒ 2(9 – 2v) + v = 12
⟹18 – 4v + v = 12
⇒ 18 – 3v = 12
⇒ 3v = 18 – 12
⇒ 3v = 6
⇒ v = 2
⇒ = 2
Substituting value of v in eq(3)
u = 9 – 2v
⇒ u = 9 – 2×2
⇒ u = 5
⇒ = 5
⇒
Hence,
x = ,y =
Solve the following equations by substitution method.
In such questions , if we start question directly, then it will involve LCM of x and y, and a term of xy, which will be inconvenient for us. So, we will assume 1/x as “u “and 1/y as v”]
+ = 7
⇒ 3u + v = 7……(1)
= 6
⇒ 5u – 4v = 6 ……..(2)
From eq(1)
v = 7 – 3u…..(3)
Substituting the value of v in eq(2)
5u – 4(7 – 3u) = 6
⇒ 5u – 28 + 12u = 6
⇒ 17u = 6 + 28
⇒ 17u = 34
⇒ u = 34/17
⇒ u = 2
⇒ = 2
Substituting the value of u in eq(3)
v = 7 – 3×2
⇒ v = 1
⇒ = 1
⇒ y = 1
Hence, x = , y = 1
Find two numbers whose sum is 24 and difference is 8.
Let the two numbers be x and y.
Since, it is given that their sum is 24,
We can write, x + y = 24
For forming second equation, we will use their difference, which is 8.
So, we can write,
x – y = 8
(we can assume any number to be greater. Here, we assumed the greater number is x)
Here, coefficient of y is equal in magnitude and opposite in sign.
So, if we add the above two equations, it will be eliminated.
Adding equation (1)and(2)
We get
2x = 32
⇒ x =
⇒ x = 16
Substituting the value of x in eq(1)
We get
x + y = 24
⇒ 16 + y = 24
⇒ y = 24 – 16
⇒ y = 8
Hence, the two required numbers are 16 and 8.
A number consists of two digits whose sum is 9. The number formed by reversing the digits exceeds twice the original number by 18. Find the original number.
Let unit digit of the number be x and its ten’s digit be y.
Then the number will be 10×y + x = 10y + x
Sum of its digits is 9.
Therefore, the sum of x and y is 9
x + y = 9……(1)
On reversing the number, ten’s digit will become unit’s digit and unit’s digit will become ten’s digit.
So, after reversing the number,
Its ten’s digit = x and unit’s digit = y
Therefore, the new number formed = 10x + y
New number formed exceeds the twice the original number by 18
⇒ 10x + y = 2(10y + x) + 18
⇒ 10x + y = 20y + 2x + 18
⇒ 8x – 19y = 18…..(2)
From equation(1),
x + y = 9
⇒ x = 9 – y…..(3)
Substituting the value of x in eq(2)
8(9 – y) – 19y = 18
⇒ 72 – 8y – 19y = 18
⇒ – 27y = 18 – 72
⇒ – 27y = – 54
⇒ y = 2
Substituting the value of y in eq(3)
x = 9 – 2
⇒ x = 7
Hence, the original number is 10y + x = 10×2 + 7 = 27
Kavi and Kural each had a number of apples. Kavi said to Kural “If you give me 4 of your apples, my number will be thrice yours”. Kural replied, “If you give me 26, my number will be twice yours”. How many did each have with them?.
Let Kavi has x apples and Kural has y apples.
According to Kavi’s statement,
We can write
x + 4 = 3(y – 4)
x + 4 = 3y – 12
⇒ x = 3y – 16…..(1)
According to Kural’s statement
y + 26 = 2(x – 26)
y + 26 = 2x – 52…….(2)
Substituting the value of x from eq(1) in eq(2)
y + 26 = 2(3y – 16) – 52
⇒ y + 26 = 6y – 32 – 52
⇒ y + 26 = 6y – 84
⇒ 5y = 110
⇒ y = 22
Substituting value of y in eq(1)
x = 3×22 – 16
⇒ x = 50
Hence, Kavi has 50 apples and Kural has 22 apples.
Solve the following inequations.
(i) 2x + 7>15
(ii) 2(x – 2) < 3
(iii) 2(x + 7) ≤ 9
(iv) 3x + 14 ≥ 8
(i) 2x + 7>15
2x>15 – 7
⇒ 2x>8
⇒ x>
⇒ x>4
(ii) 2x – 4<3
⇒ 2x>3 + 4
⇒ 2x>7
⇒ x>7/2
(iii) 2(x + 7)≤9
⇒ 2x + 14≤9
⇒ 2x≤9 – 14
⇒ 2x≤ – 5
(iv) 3x + 14≥8
⇒ 3x≥8 – 14
⇒ 3x≥ – 6
⇒ x≥
⇒ x≥ – 2
The expansion of (x + 2)(x – 1) is
A. x2 – x – 2
B. x2 + x + 2
C. x2 + x – 2
D. x2 – x + 2
Using identity,
(x + a)(x + b) = x2 + (a + b)x + ab
We have,
(x + 2)(x – 1)
= x2 + (2 – 1) x + (2x – 1) = x2 + x – 2
The expansion of (x + 1)(x – 2)(x + 3) is
A. x3 + 2x2 – 5x – 6
B. x3 – 2x2 + 5x – 6
C. x3 + 2x2 + 5x – 6
D. x3 + 2x2 + 5x + 6
Using identity,
(x + a)(x + b)(x + c) = x3 + (a + b + c)x2 + (ab + bc + ca)x + abc
We have,
(x + 1)(x – 2)(x + 3) = x3 + (1 – 2 + 3)x2 + (– 2 – 6 + 3)x – 6
= x3 + 2x2 – 5x – 6
(x – y)(x2 + xy + y2) is equal to
A. x3 + y3
B. x2 + y2
C. x2 – y2
D. x3 – y3
(x – y)(x2 + xy + y2) is simply the expansion of x3 – y3.
we can also obtain this result by multiplying them
i.e. (x – y)(x2 + xy + y2) = x(x2 + xy + y2) – y(x2 + xy + y2)
= x3 + x2y + xy2 – x2y – xy2 – y3
= x3 – y3
Factorization of x2 + 2x – 8 is
A. (x + 4)(x – 2)
B. (x – 4)(x + 2)
C. (x + 4)(x + 2)
D. (x – 4)(x – 2)
Suppose (x + p)(x + q) are two factors of x2 + 2x – 8.
Then, x2 + 2x – 8 = (x + p)(x + q)
= x2 + (p + q)x + pq
So, to factorize we have to find p and q, such that pq = – 8 and p + q = 2.
∴ x2 + 2x – 8 = (x + 4)(x – 2)
If one of the factors of x2 – 6x – 16 is (x + 2) then other factor is
A. x + 5
B. x – 5
C. x + 8
D. x – 8
Let the other factor be (x + p)
Then, x2 – 6x – 16 = (x + p)(x + 2)
= x2 + (p + 2)x + 2p
On comparing the coefficients on both sides, we get,
p + 2 = – 6
⇒ p = – 8
∴ The other factor is (x – 8).
If (2x + 1) and (x – 3) are the factors of ax2 – 5x + c, then the values of a and c are respectively
A. 2, 3
B. – 2, 3
C. 2, – 3
D. 1, – 3
ax2 – 5x + c = (2x + 1)(x – 3)
= 2x2 – 6x + x – 3
= 2x2 – 5x – 3
On comparing the coefficients on both the sides, we get,
a = 2 and c = – 3
If x + y = 10 and x – y = 2, then value of x is
A. 4
B. – 6
C. – 4
D. 6
x + y = 10
⇒ y = 10 – x substituting this value in x – y = 2
We get,
x – (10 – x) = 2
⇒ 2x – 10 = 2
⇒ 2x = 12
⇒ x = 6
The solution of 2 – x <5 is
A. x > – 3
B. x < – 3
C. x > 3
D. x < 3
2 – x <5
Adding x on both the sides,
2 <5 + x
⇒ – 3 < x
⇒ x > – 3