Question

$(x - y )^2 - x(x - 2y) \\ a(a + 2b) - (a + b)^{2}$

Answer 1

(x-y)²-x*(x-2y)=x²-2xy+y²-x²+2xy=y².
a*(a+2b)-(a+b)²=a²+2ab-a²-2ab-b²=-b².

Answer 2

(x-y)²-x*(x-2y)=x²-2xy+y²-x²+2xy=y²
a*(a+2b)-(a+b)²=a²+2ab-(a²+2ab+b²)=a²+2ab-a²-2ab-b²=-b²