## Precalculus (6th Edition) Blitzer

$$|z|=4$$
We plot the complex number $z=4$ the same way we plot $(4,0)$ in the rectangular coordinate system. We find the absolute value of the complex number as follows.$$|z|=|a+bi|=\sqrt{a^2+b^2} \\ \Rightarrow \quad |z|=|4+0i|=\sqrt{4^2+0^2}=4$$