Question

Докажите что верно равенство
(x-y)(x+y)-(a-x-y)(a-x+y)-a(2x-a)=0

Answer 1

(x-y)(x+y)-(a-x-y)(a-x+y)-a(2x-a) =

x^2 - y^2 - a^2 + ax - ay + ax - x^2 + xy + ay - xy + y^2 - 2ax +a^2 =

= 0

Answer 2

x^2-y^2-(a^2-ax+ay-ax+x^2-xy-ay+xy-y^2)-2ax+a^2=0
x^2-y^2-a^2+2ax-x^2+y^2-2ax+a^2=0
0=0