Geometric Formulas
$$ p = 2l + 2w $$
$$ A = lw $$
$$ p = 4s $$
$$ A = s^2 $$
$$ A = \frac{1}{2}bh $$
$$ a^2 + b^2 = c^2 $$
Quadratic Formula
$$ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} $$
where $$ ax^2 + bx + c = 0 $$ and $$ a \neq 0 $$