Question

已知A=5x的平方y-3xy的平方+4xy 、、B=7xy的平方-2xy+x的平方y 求负二分之一×（A+B）-A

Answer 1

由A=5x*2y-3xy*2+4xy,B=7xy*2-2xy+x*2y
得，A+B=6x*2y+4xy*2+2xy
则，所求的式子可转化为
-0.5x(6x*2y+4xy*2+2xy ) -5x*2y-3xy*2+4xy
= -3x*3y-2x*2y*2-x*2y-5x*2y-3xy*2+4xy
=-3x*3y-2x*2y*2-6x*2y-3xy*2+4xy

追问

- -貌似不对....不过谢谢，我已经写出来了~辛苦了~

Answer 2

解：-1/2×﹙A﹢B﹚﹣A=-3/2A-1/2B=-3/2(5x²y-3xy²+4xy)-1/2(7xy²-2xy+x²y)=-13/2x²y+xy²+5/8xy