Question

Expand. 

i. (5x – 7) (5x – 9) 

ii. (2x – 3y)³

iii. (a + (1/2))³

Answer 1

i. (5x – 7) (5x – 9) 

= (5x)² + (-7 -9) 5x + (-7) × (-9). …[∵ (x + a) (x + b) = x² + (a + b)x + ab] 

= 25x² + (-16) × 5x + 63 = 25x² – 80x + 63

ii. Here, a = 2x and b = 3y(2x – 3y)³ 

= (2x)³ – 3 (2x)² (3y) + 3 (2x) (3y)² – (3y)³ …[∵ (a – b)³ = a³ – 3a²b + 3ab² – b³] 

= 8x³ – 3 (4x²) (3y) + 3 (2x) (9y²) – 27y³ = 8x³ – 36x²y + 54xy² – 27p³

iii. Here, A= a and B = (1/2)