已知A=8x2y-6xy2-3xy,B=7xy2-2xy+5x2y,若A+B-3C=0,求C-A.

问题描述:

已知A=8x2y-6xy2-3xy,B=7xy2-2xy+5x2y,若A+B-3C=0,求C-A.

由题意得:3C=A+B=8x2y-6xy2-3xy+7xy2-2xy+5x2y=13x2y+xy2-5xy,
∴C=

13x2y+xy2−5xy
3

故:C-A=
13x2y+xy2−5xy
3
-(8x2y-6xy2-3xy),
=
13x2y+xy2−5xy
3
-8x2y+6xy2+3xy,
=-
11
3
x2y+
19
3
xy2+
4
3
xy.