Question

$(x-y) ^{2} = x^{2}+ y^{2}$

Answer 1

(x-y)²=x²+y²
x²-2xy+y²=x²+y²
x²-x²-2xy+y²-y²=0
-2xy=0
xy∈Ф din cate stiu eu zero impartit la orice numar nu are sens

Answer 2

$(x-y)^2=x^2+y^2 \Longleftrightarrow x^2-2xy+y^2=x^2+y^2 \Longleftrightarrow xy=0\Rightarrow x=0,y\in \mathbb{R}$ sau invers.