Answer:
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
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