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:
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:
$ on either side of math, as in $1+2$
^ for superscripts and _ for subscripts, with { } to group multiple characters, as in $3^{1+2}$ for $3^{1+2}$\frac{ }{ } for fractions, as in $\frac{4}{5}$ for $\frac{4}{5}$\alpha, \beta, ... for greek letters$$\frac{ x_{n+1} + \alpha }{ x_n + \beta } = \gamma^3$$ would render like this:
$$\frac{ x_{n+1} + \alpha }{ x_n + \beta } = \gamma^3$$
$\LaTeX$