Question

(x-y) (x+y) - a(2x-a)-(a-x+y)(a-x-y)=0​

Answer 1

Ответ:

$(x-y)(x+y)-a(2x-a)-(a-x+y)(a-x-y)=\\\\=x^2-y^2-2ax+a^2-\Big((a-x)+y\Big)\Big((a-x)-y\Big)=\\\\=x^2-y^2-2ax+a^2-\Big((a-x)^2-y^2\Big)=\\\\=x^2-y^2-2ax+a^2-\Big(a^2-2ax+x^2-y^2\Big)=\\\\=x^2-y^2-2ax+a^2-a^2+2ax-x^2+y^2=0$