题目

化简求值：X的平方-y的平方分之2x-x-y分之1 其中x=3倍的根号5-1 y=-2倍的根号5+1

提问时间：2020-07-24

答案

原式=2x/(x+y)(x-y)-(x+y)/(x-y)(x+y)
=(2x-x-y)/(x+y)(x-y)
=(x-y)/(x+y)(x-y)
=1/(x+y)
=1/(3√5-1-2√5+1)
=1/√5
=√5/5