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
.
=a-b+c-d,试计算
.
xy-3x2 -2xy-x2
-2x2-3 -5+xy
.

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.