3/（(x-2)(x+1)）-（1/（x-2））=3/（(x-2)(x+1)）-（x+1)/（x-2）(x+1）=(3-x-1)/(（x-2）(x+1）=(2-x)/（x-2）(x+1）=-1/(x+1)2/（a²-1）+1/（a+1）=2/（a²-1）+(a-1)/（a+1）(a-1)=(2+a-1)/(（a²-1）=(a+1)/(（a²-1）=1/(a-1)x/(2-x)-(4-x²)/(x²-4x+4)=-x(x-2)/(x²-4x+4)-(4-x²)/(x²-4x+4)=(-x²+2x-4+x²)/(x²-4x+4)=-2(x-2)/(x²-4x+4)=-2/(x-2)=2/(2-x)