原式＝(2-2b)x^2+(a+3)x-6y+7
(2x^2+ax-y+6)-(2bx^2-3x+5y-1)的值与字母x所取值无关,所以
a+3＝0
2-2b＝0
a=-3
b=1,
a^2/3-2b=3-2=1