Question

Use the formula to multiply the following :

i. (x + y)(x – y) 

ii. (3x – 5)(3x + 5) 

iii. (a + 6)(a – 6)

iv. \((\frac{x}{5} + 6) (\frac{x}{5} - 6)\)

Answer 1

i. Here, a = x, b = y 

(x + y)(x – y) = x² – y² 

…. [(a + b)(a – b) = a² – b^{​​​​​​​2}]

ii. Here, a = 3x, b = 5

(3x – 5) (3x + 5) = (3x)² – 5² 

…. [(a + b)(a – b) = a² – b²] 

= 9x² – 25

iii. Here, A = a, B = 6 

(a + 6) (a – 6) = a² – 6²

…. [(A + B)(A – B) = A² – B²] 

= a² – 36

iv. Here, a = x/5, b = 6