Question

Use the formula to multiply the following: 

i. (x + y)(x – y) 

ii. (3x – 5)(3x + 5) 

iii. (a + 6)(a – 6

iv. (x/5 + 6) (x/5 - 6)

Answer 1

i. Here, a = x, b = y 

(x + y)(x – y) = x² – y²  …. [(a + b)(a – b) = a²  – b² ]

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/2 , b = 6 

(x/5 + 6) (x/5 - 6) = (x/5)² - (6)²…. [(a + b)(a – b) = a²  – b² ]

= x² /25 - 36