Some MathJax frequently used here:

Equation in-line: `\$123\$` \$\rightarrow\$ \$123\$

Equation centered on a separate line: `$$123$$` \$\rightarrow\$ $$123$$

Fractions:  1/2 \$\rightarrow\$ `\$\frac{1}{2}\$` \$\rightarrow\$ \$\frac{1}{2}\$

Bigger fractions:  1/2 \$\rightarrow\$ `\$\dfrac{1}{2}\$` \$\rightarrow\$ \$\dfrac{1}{2}\$

Something enclosed by full parentheses: (1/2) \$\rightarrow\$ `\$\left(\frac{1}{2}\right)\$` \$\rightarrow\$ \$\left(\frac{1}{2}\right)\$

Exponent: I^2 \$\rightarrow\$ `\$I^2\$` \$\rightarrow\$ \$I^2\$

Exponent: e^-1 \$\rightarrow\$ `\$e^{-1}\$` \$\rightarrow\$ \$e^{-1}\$

Subscript: t0 \$\rightarrow\$ `\$t_0\$` \$\rightarrow\$ \$t_0\$

Removing the italics from previous: \$\rightarrow\$ `\$\$\text{t}_0\$` \$\rightarrow\$ \$\text{t}_0\$

Square Root: sqrt(9) \$\rightarrow\$ `\$\sqrt{9}\$` \$\rightarrow\$ \$\sqrt{9}\$

Greek symbols: \$\rightarrow\$ `\$\alpha \beta \delta \Delta \omega \Omega \rho\$` \$\rightarrow\$ \$\alpha \beta \delta \Delta \omega \Omega \rho\$