Question

（x+5）/[(x+1)(x-3)]=A/(x+1)-B/(x-3),求A、B

Answer 1

待定系数法.

（x+5）/[(x+1)(x-3)]=A/(x+1)-B/(x-3)

得到：（x+5）/[(x+1)(x-3)]=[（A-B)x+(-3A-B)]/[(x+1)(x-3)]

A-B=1

-3A-B=5

所以,A=-1 B=-2