先化简再求值X-1分之2-X除以(X+1-X-1分之3),其中X=-3

问题描述:

先化简再求值X-1分之2-X除以(X+1-X-1分之3),其中X=-3

原式=-(x-2)/(x-1)÷(x²-1-3)/(x-1)
=-(x-2)/(x-1)*(x-1)/(x+2)(x-2)
=-1/(x+2)
=-1/(-3+2)
=1=-(x-2)/(x-1)*(x-1)/(x+2)(x-2)这一步不太明白÷变成乘