(2x ^2+ax-y+b)-(2bx^2-3x+5y-1)的值与x取值无关,求(3a^2-ab-b^2)-(4a^2+ab+b^2)的值

问题描述:

(2x ^2+ax-y+b)-(2bx^2-3x+5y-1)的值与x取值无关,求(3a^2-ab-b^2)-(4a^2+ab+b^2)的值

(2x ^2+ax-y+b)-(2bx^2-3x+5y-1)=2x ^2+ax-y+b-2bx^2+3x-5y+1=(2-2b)x ^2+(a+3)x-6y+b+1和x无关则x系数为0所以2-2b=0,a+3=0a=-3,b=1所以原式=3a²-ab-b²-4a²-ab-b²=-a²-2ab-2b²=-9+6-2...