设k=a+b−cc=a−b+cb=−a+b+ca,则k的值为_.

问题描述:

设k=

a+b−c
c
=
a−b+c
b
=
−a+b+c
a
,则k的值为______.

当a+b+c≠0时,∵

a+b−c
c
=
a−b+c
b
=
−a+b+c
a

a+b−c
c
=
a−b+c
b
=
−a+b+c
a
=
a+b−c+a−b+c−a+b+c
a+b+c
=k=
a+b+c
a+b+c
=1
当a+b+c=0时,即a+b=-c,所以k=
a+b−c
c
=
−c−c
c
=-2
所以k的值为1或-2.