化简求值:[(x-2y)2-4y2+2xy]÷2x,其中x=1,y=2.

问题描述:

化简求值:[(x-2y)2-4y2+2xy]÷2x,其中x=1,y=2.

∵x=1,y=2,
∴[(x-2y)2-4y2+2xy]÷2x=(x2-4xy+4y2-4y2+2xy)÷2x
=(x2-2xy)÷2x
=

1
2
x-y
=
1
2
×1
-2
=-
3
2