Respuesta :

ghanami

Answer:

x+y=4

Step-by-step 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

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