b/a−b+c+2a+c/b−a−c-b−cb−a−c

问题描述:

b
a−b+c
+
2a+c
b−a−c
-
b−c
b−a−c

b
a−b+c
+
2a+c
b−a−c
b−c
b−a−c

=
b
a−b+c
+
2a+c−b+c
b−a−c
−b
b−a−c
+
2a−b+2c
b−a−c
2a−2b+2c
b−a−c
=-2.