现规定.abcd.=a-b+c-d,试计算.xy-3x2-2xy-x2-2x2-3-5+xy..
问题描述:
现规定
=a-b+c-d,试计算
.
a
b
c
d
.
.
.
xy-3x2
-2xy-x2
-2x2-3
-5+xy
.
答
由题意得:
=(xy-3x2)-(-2xy-x2)+(-2x2-3)-(-5+xy)
.
xy-3x2
-2xy-x2
-2x2-3
-5+xy
.
=xy-3x2+2xy+x2-2x2-3+5-xy
=2xy-4x2+2.