Question

Given that x2 - y2 = 135 and x - y = 15 , find the value of (x+y)2

Answer 1

x² - y² = 135

<=> (x - y)(x + y) = 135

<=> 15(x + y) = 135

=> x + y = 135/15 = 9

=> (x + y)² = 81