(2x^2+ax-y+6)-(2bx^2-3x+5y-1)=2x²+ax-y+6-2bx²+3x-5y+1
=(2-2b)x²+(a+3)x-6y+7
与x无关
那么2-2b=0
b=1
a+3=0
a=-3
1/2a²-2b+4ab=1/2×9-2×1-4×1×3=4.5-2-12=9.5你这...........真慢死我了...........