绝对值x+3=-(2x+y)的平方
绝对值x+3+(2x+y)的平方=0
x=-3 2x+y=0 y=-2x=6
3/4x^2-3y+1/4x^2+y
=x^2-3y+y
=(-3)^2-3*6+6
=9-18+6
= -3