Useful links for Mathematics Stack Exchange:

https://math.meta.stackexchange.com/questions/9959/how-to-ask-a-good-question

In particular, to increase your chances of having your question answered instead of closed, explain the context of your problem, state it clearly, show your attempt at solving it, and explain where you are stuck or confused.

DO NOT simply write a question with "PLZ HELP!"

https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference

To get started, try:

1. putting $ on either side of math (two $$ on either side for "equation mode")
2. using ^ for superscripts and _ for subscripts, with { } to group multiple characters
3. using \frac{ }{ } for fractions
4. using \alpha, \beta, ... for greek letters

$$\frac{ x_{n+1} + \alpha }{ x_n + \beta } = \gamma^3$$ would render like this:

$$\frac{ x_{n+1} + \alpha }{ x_n + \beta } = \gamma^3$$