(2x²+ax-y)-(bx²-3x+5y-1)
=(2-b)x²+(a+3)x-6y+1
因为该式与x的取值无关
所以x²和x前面的系数为0
即2-b=0,a+3=0
那么a=-3,b=2
3(a²-2ab-b²)-(4a²+ab+b²)
=-a²-7ab-4b²
=-(-3)²-7×(-3)×2-4×2²
=17(a+2)²+|3b-1|=0所以a+2=0,3b-1=0a=-2,b=1/33a²b+[2ab²-6(ab-1/2a²b)+4ab]-2ab=ab(3a+2b-6+3a+4-2)=ab(6a+2b-4)=-2/3×(-12+2/3-4)=92/9