原式=1/2x-(2x-2/3y²+3/2x-1/3y²)
=1/2x-(7/2x-y²)
=1/2x-7/2x+y²
=-3x+y²
=-3×1/4+(-1)²
=1/4дһ�µ�x=1/4ʲô����x=1/4��y=-1ԭʽ=-3��1/4+(-1)²