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已知x-y=1,求x2-y2+x-3y的值.
人气:244 ℃ 时间:2020-01-27 00:36:48
解答
∵x-y=1,
∴x2-y2+x-3y
=(x+y)(x-y)+x-3y,
=x+y+x-3y,
=2x-2y,
=2(x-y),
=2.
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