右边通分 =[A(x-3)+B(x-1)]/(x-1)(x-3) =[(A+B)x-(3A+B)]/(x-1)(x-3) =(2x-8)/(x-1)(x-3) 所以(A+B)x-(3A+B)=2x-8 所以 A+B=2 3A+B=8 所以 A=3.B=-1
