> 数学 >
当x=2,y=
1
2
时,求代数式(x+y)(x-y)+(x-y)2-(x2-3xy)的值.
人气:115 ℃ 时间:2019-09-29 01:21:56
解答
(x+y)(x-y)+(x-y)2-(x2-3xy),
=x2-y2+x2-2xy+y2-x2+3xy,
=x2+xy,
当x=2,y=
1
2
时,原式=22+2×
1
2
=5.
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