x y满足等式2(x-2分之1的2次方)+y-1决对值=0
则x-2分之1=0,y-1=0
则x=2分之1,y=1
3b-2a
=3*(2x的2次方)-2*(3x的2次方-xy+y的2次方)
=6x²-6x²+2xy-2y²
=2xy-2y²
=2y(x-y)
=2×1×(2分之1-1)
=2×(-2分之1)
=-1