4a-1/(a+2)(a-1)=x/a+2+y/a-1,求x,y的值

4a-1/(a+2)(a-1)
=(4a-1)/(a+2)-(4a-1)/(a-1)
=(4a-1)/(a+2)+(1-4a)/(a-1)
所以
x=4a-1
y=1-4a

原等式可化成
(4a-1)/[(a+2)(a-1)]
=[2x(a-1)+y(a-2)]/[(a+2)(a-1)]
=[(2x+y)a-(2x-2y)]/[(a+2)(a-1)]
左右两边相等，故
2x+y=4
2x-2y=1
解方程组，得x=3/2，y=1