(2x²+ax-y+b)-(2bx²-3x+5y-1)
=2x²+ax-y+b-2bx²+3x-5y+1
=(2-2b)x²+(a+3)x-6y+b+
与字母x的取值无关则含x的项系数为0
2-2b=0,a+3=0
a=-3,b=1