已知x/y=3,求x2+2xy−3y2x2−xy+y2.

问题描述:

已知

x
y
=3,求
x2+2xy−3y2
x2−xy+y2

x
y
=3,得到x=3y,
则原式=
9y2+6y2−3y2
9y2−3y2+y2
=
12
7