如果x＞y＞0,x的x次方乘以y的y次方分之x的y次方乘以y的x次方等于

(x^y×y^y)/(x^x×y^y)
=x^(y-x)×y^(x-y)
因为x＞y＞0
原式=x^-(x-y)×y^(x-y)
=[y^(x-y)]/[x^(x-y)]
=(y/x)^(x-y)