|x-1/2x-3|+(3y+1/y+4)^2=0
两个非负数之和为0,那么这两个数都是0
(x-1)/(2x-3)=0
x=1
(3y+1)/(y+4)=0
y=-1/3
3/(2-3)-3/(-1-1)
=-3+3/2
=-3/2