Conceptual tests.

$$x = 2$$

Here is undisplayed span (see Ctrl+U) which replaces MathJax speech for following expression. This is a very complex formula: Y is equal to 4. $$ y = 1+1+1+1+1 $$

Quadratic equation solution:

$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$

Footnote.