2x²+ax-y+6-(2bx²-3x+5y-1)
=2x²+ax-y+6-2bx²+3x-5y+1
=(2x²-2bx²)+(ax+3x)+(-y-5y)+(6+1)
=(2-2b)x²+(a+3)x-6y+7
因?yàn)椴钆c字母x的取值無關(guān),所以含有字母x的項(xiàng)的系數(shù)都為0
所以有：
2-2b=0且a+3=0
a=-3,b=1
a²b-(6ab+3a²b)+(5ab+2a²b)
=a²b-6ab-3a²b+5ab+2a²b
=(a²b-3a²b+2a²b)+(-6ab+5ab)
=0+(-ab)
= -ab 把a(bǔ)=-3,b=1代入
=-(-3)×1
=-(-3)
=3