Respuesta :

mumsy
x^2-y^2=55
this means that 
(x+y)(x-y)=55
we know that x-y=11 so we can write
(x+y)(11)=55
x+y=55/11 we divide by 11 and we obtain 
x+y=5

x-y=11 this means
x=y+11 we replace in the other equation (x+y=5)

y+11+y=5
2y=5-11
2y=-6
y=-3
and you find out that also 
x=8

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