3x²+axy-2y²+1-(2bx²-3xy+y²)
=3x²+axy-2y²+1-2bx²+3xy-y²
=(3-2b)x²+(a+3)xy-3y²+1
∵该式值与x的取值无关
∴3-2b=0且a+3=0
∴b=3/2,a=-3
∴2(a²-2ab+b²)-3
=2(a-b)²-3
=2(-3-3/2)²-3
=2×81/4-3
=37.5
3x²+axy-2y²+1-(2bx²-3xy+y²)
=3x²+axy-2y²+1-2bx²+3xy-y²
=(3-2b)x²+(a+3)xy-3y²+1
∵该式值与x的取值无关
∴3-2b=0且a+3=0
∴b=3/2,a=-3
∴2(a²-2ab+b²)-3
=2(a-b)²-3
=2(-3-3/2)²-3
=2×81/4-3
=37.5