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.

[latex]x = \frac {a} {bcd}[/latex]

[latex]\boldsymbol { x = \sqrt {45 +y^3 } }[/latex]

[latex]Force_{gravity} = G \frac {m_1 m_2} {r^2}[/latex]

This is what it looks like in the Admin mode.