Equations, Inequalities and Graphs includes quadratic inequalities and the modulus (absolute value).
The modulus $|x|$ is the size of $x$ ignoring its sign, so $|-7|=7$. The equation $|x|=5$ has two solutions, $x=5$ and $x=-5$.
Remember
- $|x|$ is always $\ge 0$.
- $|x|=k$ (for $k>0$) has two solutions.