Question

mathematica解符号变量方程

A + B + C == 0,
A (b + c) + B (a + c) + C (a + b) == 0,
Abc + Bac + Cab == 1
三个方程联立要解出A，B，C来，而且A，B，C的符号表达式完全由a，b，c表示。

Answer 1

In[23]:= Solve[{A + B + C1 == 0,
A (b + c) + B (a + c) + C1 (a + b) == 0,
A b c + B a c + C1 a b == 1}, {A, B, C1}]

{{A -> -(1/((-a + b) (a - c))), B -> -(1/((a - b) (b - c))),
C1 -> -(1/((a - c) (-b + c)))}}

记得加空格，否则连写则认为是一个变量名。