Simple equations can be used with the word processing features.

ax² + bx + c = 0           or          x = a/b.

You can add special characters such as the Greek alphabet

sin θ = 1.00               θ = 45.0 degrees = 45.0°                   5.67 Ω

LaTeX

For more complex equations you want to use LaTeX.

https://www.latex-project.org/

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

[latex]x = \dfrac {a} {b}[/latex]

You can bold them.

[latex]\boldsymbol{ x = \dfrac {a} {b } }[/latex]

[latex]\boldsymbol{ x = \sqrt {y} }[/latex]

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

[latex]\int_a^b x^2 dx[/latex]

[latex]\displaystyle\int_{a}^{b} x^2 dx[/latex]

[latex]\displaystyle\int\limits_{a}^{b} x^2 dx[/latex]

[latex]F = m \dfrac{d^2x}{dt^2}[/latex]

[latex]\vec{A}_{\text{x}} = \dfrac{\partial f(x)}{\partial x}[/latex]

[latex]\tan\theta = \dfrac{\sin{\theta}}{\cos{\theta}}[/latex]

This is what it looks like in the Admin mode.  I just did a screen capture and then cut and pasted it into the book.