Question

(5х-7у)^2-(7х-5у)^2 Помогите решииить 

Answer 1

( (5х)^2-2*5х*7у+(7у)^2 ) - ( (7х)^2-2*7х*5у+(5у)^2 ) = 25х^2-70ху+49у^2-49х^2+70ху-25у^2 = -24х^2-24у^2