已知(2x+3)÷(x(x+2)(x-1))=(A/x)+ (B/(x-1))+ (C/(x+2)) 求常数A 、B、C、的值

题目

已知(2x+3)÷(x(x+2)(x-1))=(A/x)+ (B/(x-1))+ (C/(x+2)) 求常数A 、B、C、的值

答案

(2x+3)÷[x(x-1)(x+2)]=A÷x+B÷(x-1)+C÷(x+2)
2x+3=A*(x-1)(x+2)+B*x(x+2)+C*x(x-1)
2x+3=A(x^2+x-2)+B(x^2+2x)+C(x^2-x)
2x+3=(A+B+C)x^2+(A+2B-C)x-2A
A+B+C=0
A+2B-C=2
-2A=3
解方程组得：
A=-3/2,B=5/3,C=-1/6