化简求值: [(x+2y)2-(x-2y)2-(x+2y)(x-2y)-4y2]÷2x,其中x=-2,y=1/2.
化简求值:
[(x+2y)
2-(x-2y)
2-(x+2y)(x-2y)-4y
2]÷2x,其中x=-2,y=
.
数学人气:742 ℃时间:2019-08-17 22:39:30
优质解答
[(x+2y)
2-(x-2y)
2-(x+2y)(x-2y)-4y
2]÷2x,
=[(x
2+4xy+4y
2)-(x
2-4xy+4y
2)-(x
2-4y
2)-4y
2]÷2x,
=(x
2+4xy+4y
2-x
2+4xy-4y
2-x
2+4y
2-4y
2)÷2x,
=(-x
2+8xy)÷2x,
=-
x+4y,
当x=-2,y=
时,
原式=-
×(-2)+4×
=1+2=3.
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