Q8 of 59 Page 38

Use the identity (a + b)(a – b) = a2 – b2 to find the products:

(i) (x – 6) (x + 6)


(ii) (3x + 5)(3x + 5)


(iii) (2a + 4b)(2a – 4b)


(iv)

The given identity is (a+b) (a–b) = a2 –b2

(i) (x – 6) (x + 6)


Using the given identity


Here a = x and b = 6


= x2 – 62


= x2 – 36


(ii) (3x + 5)(3x + 5)


Using the given identity


Here a = 3x and b = 5


= (3x)2 – 52


= 9x2 – 25


(iii) (2a + 4b)(2a – 4b)


Using the given identity


Here a = 2a and b = 4b


= (2a)2 – (4b)2


= 4a2 – 16b2


(iv)


Using the given identity


Here



=


More from this chapter

All 59 →
6

Use the identity (a – b)2 = a2 – 2ab + b2 to compute:

(i) (x – 6)2 (ii) (3x – 5y)2


(iii) (5a – 4b)2 (iv) (p2 + q2)2

 7

Evaluate using the identity (a – b)2 = a2 – 2ab + b2

(i) (49)2 (ii) (9.8)2


(iii) (59)2 (iv) (198)2

 9

Evaluate these using identity:

(i) 55 × 45 (ii) 33 × 27


(iii) 8.5 × 9.5 (iv) 102 × 98

 10

Find the product:

(x – 3)(x + 3)(x2 + 9)