题目

（1）12/a²-9+2/3-a+2/a+3 （2）x/x-1-3/（x-1)（x+2）-1

提问时间：2020-12-05

答案

（1）12/(a²-9)+2/(3-a)+2/(a+3)
=12/(a²-9) - 2/(a-3)+2/(a+3)
=12/(a²-9) + 2[(a-3)-(a+3)]/[(a-3)/(a+3)]
=12/(a²-9)-12/(a²-9)
=0
（2）x/(x-1)- 3/(x-1)(x+2)-1
=x(x+2)/(x-1)(x+2)- 3/(x-1)(x+2)-1
=(x²+2x-3)/(x-1)(x+2) -1
=(x+3)(x-1)/(x-1)(x+2) -1
=(x+3)/(x+2) -1
=(x+3-x-2)/(x+2)
=1/(x+2)