先化简再求值[(x+y)2-(x+y)(x+3y)-4y2]÷2y,其中x=-2,y=1/2.
先化简再求值[(x+y)
2-(x+y)(x+3y)-4y
2]÷2y,其中x=-2,
y=.
数学人气:388 ℃时间:2020-02-03 11:12:06
优质解答
[(x+y)
2-(x+y)(x+3y)-4y
2]÷2y,
=[x
2+2xy+y
2-x
2-3xy-xy-3y
2-4y
2]÷2y
=(-2xy-6y
2)÷2y
=-x-3y,
当x=-2,
y=时,
原式=-(-2)-3×
=
.
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