# Solve equations and express with specific varible

I have two equations as below:

eq1: $8 \pi \gamma r-\frac{4 \pi \text{Delta$\_\mu $} r^2}{\text{v$\_$c}}=0$

eq2: $\text{Delta$\_\mu $}=\text{K$\_$b} S T$

When I try Solve[{eq1}, {r}], I obtained $\left\{\{r\to 0\},\left\{r\to \frac{2 \gamma \text{v$\_$c}}{\text{Delta$\_\mu $}}\right\}\right\}$.

This is correct, but I want it is expressed as $\left\{r\to \frac{2 \gamma \text{v$\_$c}}{\text{K$\_$b} S T}\right\}$. I tried Solve[{eq1, eq2}, {r}] but I obtained {}

How can I get the result expressed with K_b, S and T instead of Delta_u? Many thanks!

• it is better to post the actual Mathematica plain source code you used. Also _ can't be used in variable names. – Nasser Dec 21 '15 at 11:03
• Try Eliminate. – Sjoerd C. de Vries Dec 21 '15 at 11:11
• Or Solve for both Delta_u and r (I trust the actual "variable" does not have an underbar in it). – Daniel Lichtblau Dec 21 '15 at 16:10

Format[v[c]] := Subscript[v, c];