(ax²-2xy+y²)-(-ax²+bxy+2y²)=8x²-7xy-cy²成立,求a,b,c.

(ax²-2xy+y²)-(-ax²+bxy+2y²)=8x²-7xy-cy²成立,求a,b,c.
(ax²-2xy+y²)-(-ax²+bxy+2y²)=8x²-7xy-cy²成立,求a,b,c.

(ax²-2xy+y²)-(-ax²+bxy+2y²)=8x²-7xy-cy²成立,求a,b,c.
由于(ax²-2xy+y²)-(-ax²+bxy+2y²)=2ax²-(2+b)xy-y²=8x²-7xy-cy²；
若欲使上面等式成立,需满足
2a=8,-(2+b)=-7,-c=-1 ；
解得：a=4,b=5,c=1