Question

daca x+y=5 si x²-y²=20 calculati
n a) (x+y)² b) (x-y)²

Answer 1

$x^2-y^2=20 \\ (x+y)(x-y)=20 \\ x-y=4 \\ \\ (x+y)^2=(x+y)(x+y)=5*5=25 \\ (x-y)^2=(x-y)(x-y)=4*4=16$