Huy Toàn 8A (TL)
07/07/2018 at 00:19-
Nguyễn Mạnh Hùng 07/07/2018 at 08:08\(\left(x+2y\right)^2+\left(2x-y\right)^2-\left(5x+y\right)\left(x-y\right)-10\left(y+3\right)\left(y-3\right)\)
\(=x^2+4xy+4y^2+4x^2-4xy+y^2-5x^2+5xy-xy+y^2-10\left(y^2-9\right)\)
\(=-4y^2+4xy+90\)
Huy Toàn 8A (TL) selected this answer.