Question

Given that 2x^2 - 2y^2 = 40 and x-y=5, find the value of (x+y)

Answer 1

x+y=4

Explanation:

hello :

note : by identity you have x²-y² = (x-y)(x+y)

in this exercice : 2x²-2y² = 2(x²-y²) = 2 (x-y)(x+y)

means : 2 (x-y)(x+y) = 40

but x-y = 5

so : 2(5)(x+y) =40

x+y=40/10

x+y=4