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.

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

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

$Force_{gravity} = G \frac {m_1 m_2} {r^2}$

This is what it looks like in the Admin mode.