x-1分之2÷（x²；-1分之2+x+1分之1） a²；-2a+1分之a+1÷（1+a-1分之2）

原式=2/（x-1）÷[2/（x+1）（x-1）+（x-1）/（x+1）（x-1）]=2/（x-1）÷（2+x-1）/（x+1）（x-1）=2/（x-1）×（x-1）=2原式=（a+1）/（a-1）²；÷[（a-1）/（a-1）+2/（a-1）]=（a+1）/（a-1）²；÷[（a-1）+2]/（a-1）=（a+1）/（a-1）²；×（a-1）…