A/（x-2)+B/(x-5)
=[A(x-5)+B(x-2)]/(x-2)(x-5)
=(Ax-5A+Bx-2B)/(x-2)(x-5)
=[(A+B)x+(-5A-2B)]/(x-2)(x-5)
=(4x+1)/(x-2)(x-5)
所以A+B=4
-5A-2B=1
解得
A=-3
B=7