I have a function `g[t]` and I want to add (in the x-axis, colored red for example) the point of intersection of `g[t]` with the x-axis ([g[t]==0) named `g0` , and a point `g1` that satisfy the equation `g1=g0/3`, and to add the vertical dashed line from the plot to x-axis in the `g1` point .
The function would look like this :

```
g[t_] = 1 - 1/(Exp[990/t] - 1); Plot[g[t], {t, 0, 1500}]

```

The output would look similar to:

[![enter image description here](https://i.stack.imgur.com/0CLPf.png)](https://i.stack.imgur.com/0CLPf.png)