已知:3x=2y,求代数式(2x-y)2-x(x-2y)-y2的值.
问题描述:
已知:3x=2y,求代数式(2x-y)2-x(x-2y)-y2的值.
答
(2x-y)2-x(x-2y)-y2
=4x2-4xy+y2-x2+2xy-y2
=3x2-2xy
∵3x=2y
∴原式=3x•x-2xy
=2xy-2xy
=0.