已知x+y=3,xy=-2,求(3x-2y+8xy)-(x-4y-5xy)的值.
人气:346 ℃ 时间:2019-10-19 17:24:17
解答
(3x-2y+8xy)-(x-4y-5xy)
=3x-2y+8xy-x+4y+5xy
=(3x-x)+(-2y+4y)+(8xy+5xy)
=2x+2y+13xy
=2(x+y)+13xy
=2×3+13×(-2)
=6-26
=-20
答案:-20
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