Simple equations can be used with the word processing features.

ax² + bx + c = 0

You can add special characters such as the Greek alphabet

If sin θ = 1.00,   θ = 45.0 degrees    or  5.67 Ω

LaTex

For more complex equations you want to use LaTex.

Free, open source software that writes equations that look good on the web and in print.

$x=\frac{a}{bcd}$

$\mathit{x}\mathbf{=}\sqrt{\mathbf{45}\mathbf{+}{\mathit{y}}^{\mathbf{3}}}$

$Forc{e}_{gravity}=G\frac{m_1{m}_2}{r^2}$

This is what it looks like in the Admin mode.