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若χ-2y=7,χy=3,则2χy-4y+2χ+5=多少
人气:180 ℃ 时间:2020-05-25 01:58:07
解答
2χy-4y+2χ+5
=2χy+2(x-2y)+5
=2×3+2×7+5
=25
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