题目

一、 (x-y)^5÷(y-x)^2-(x-y) 二、 先化简,后求值 (2x-y)^13-[(2x-y)^3]-[(y-2x)^2]^4 其中x=2 y=-1

提问时间：2020-10-08

答案

一、 (x-y)^5÷(y-x)^2-(x-y)
=(x-y)^5÷(x-y)^2-(x-y)
=(x-y)^3-(x-y)=(x-y)[(x-y)^2-1]
=(x-y)(x-y+1)(x-y-1)
二、 (2x-y)^13-[(2x-y)^3]-[(y-2x)^2]^4
= (2x-y)^13-(2x-y)^3-(2x-y)^8
=(2x-y)^3*[(2x-y)^10-(2x-y)^5-1]
将x=2 y=-1代入
=(4+1)^3*[(4+1)^10-(4+1)^5-1]
=125*(5^10-5^5-1)
=125*(9765625-3125-1)
=125*(9762500-1)
=1220312500-125
=1220312375