2x^2+ax-y+6=2bx^2-3x+5y-1对于任意x恒成立
则2=2b a=-3 -y+6=5y-1
解得b=1 a=-3 y=7/6
a^3/3-2b^2-(a^3/4-3b^2)
=-9-2-27/4+3
=-8-27/4=-59/4