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问题: 一道简单的数学题

已知8x2m-3yn÷(-4xmy2)=-2x,则m-n的值是多少?

解答:

8x的2m-3次方×y的n次方÷(-4x的m次方y的2次方)
= (-2) * x^(2m-3-m) * y^(n-2)
= (-2) * x(m-3) * y^(n-2)
= -2x
==> m-3 = 1, n-2 = 0
m = 4, n = 2
则: m^(-n) = 4^(-2) = 1/16