若(ax²-2xy+y²)-(-ax²+bxy+2y²)=6x²-9xy+cy²成立,abc的值非别是多少?
问题描述：
若(ax²-2xy+y²)-(-ax²+bxy+2y²)=6x²-9xy+cy²成立,abc的值非别是多少?
答
(a+2)x2-(2+b)xy+(1-2)y2=6x2-9xy+cy2
所以(a+2)x2=6x2, -(2+b)xy=9xy, (1-2)y2=cy2
所以a+2=6, -2-b=9, 1-2=c
所以a=4, b=-11, c=-1
答
(ax²-2xy+y²)-(-ax²+bxy+2y²)=6x²-9xy+cy²
2ax²+(b-2)xy-y²=6x²-9xy+cy²
2a=6 a=3
b-2=-9 b=-7
c=-1
答
(ax²-2xy+y²)-(-ax²+bxy+2y²)=6x²-9xy+cy²
2ax^2-(2+b)xy-y^2=6x²-9xy+cy²
2a=6 所以a=3
2+b=9 所以 b=7
c=-1