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RD Chapter 5 Factorisation of Algebraic Expressions Ex 5.2 Solutions

Question - 1 : - Factorize each of the following expressions:
p3┬а+ 27

Answer - 1 : -

We know that a3┬а+ b3┬а= (a + b)(a2┬атАУ ab + b2)
a3┬атАУ b3┬а= (a тАУ b) (a2┬а+ aft + b2)
p3┬а+ 21 = (p)3┬а+ (3)3
= (p + 3) (p2тАУ p x 3 + 32)
= (p + 3) (p2┬атАУ 3p + 9)

Question - 2 : - y3 + 125

Answer - 2 : -

y3┬а+ 125 = (p)3┬а+ (5)3
= (p + 5) (p2┬атАУ 5y + 52)
= (P + 5) (p2┬атАУ 5y + 25)

Question - 3 : - 1 тАУ 21a3

Answer - 3 : -

1 тАУ 21a3┬а= (1)3┬атАУ (3a)3
= (1 тАУ 3a) [12┬а+ 1 x 3a + (3a)2]
= (1 тАУ 3a) (1 + 3a + 9a2)

Question - 4 : - 8x3y3 + 27a3

Answer - 4 : -

8x3y3┬а+ 27a3
= (2xy + 3a) [(2xy)2┬атАУ 2xy x 3a + (3a)2]
= (2xy + 3a) (4x2y тАУ 6xya + 9a2)

Question - 5 : - 64a3 тАУ b3

Answer - 5 : -

64a3┬атАУ b3┬а= (4a)3┬атАУ(b)3
= (4a тАУ b) [(4a)2┬а+ 4a x b + (b)2]
= (4a тАУ b) (16a2┬а+ 4ab + b2)

Question - 6 : -

Answer - 6 : -


Question - 7 : - 10x4тАУ 10xy4

Answer - 7 : -

I0x4y-┬а10xy4┬а=┬а10xy(x3┬а-y3)
=┬а
10xy(x тАУy) (x2┬а+┬аxy + y2)

Question - 8 : - 54x6y + 2x3y4

Answer - 8 : -

54┬аx6y┬а+2x3y4┬а=┬а2x3y(27x3┬а+y3)
= 2x3y[(3x)3┬а+(y)3]
=┬а2x3y(3x┬а+y) [(3x)2┬а-3xx y + y2]
= 2x3y(3x┬а+┬аy) (9x2┬а-3xy+ y2)

Question - 9 : - 32a3 + 108b3

Answer - 9 : -

32a3┬а+ 108b3
= 4(8a3┬а+ 27b3) = 4 [(2a)3┬а+(3 b)3]
= 4(2a + 3b) [(2a)2┬атАУ 2a x 3b + (3b)2]
= 4(2a + 3b) (4a2┬атАУ 6ab + 9b2)

Question - 10 : - (a тАУ 2b)3 тАУ 512b3

Answer - 10 : -

(a тАУ 2b)3┬атАУ 512b3
= (a тАУ 2b)3┬атАУ (8b)3
= (a тАУ 2b- 8b) [(a тАУ 2b)2┬а+ (a тАУ 2b) x 8b + (8b)2]
= (a тАУ 10b) [a2┬а+ 4b2┬атАУ 4ab + 8ab тАУ 16b2┬а+64b2]
= (a тАУ 10b) (a2┬а+ 4ab + 52b2)

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