# Calculating number on the modulus

I have a problem where I had to graph a complex number in the complex plane. The problem is: Given the complex number -4 + 5i, graph the complex number in the complex plane. I did this and got 0 to -5.

The second part of the problem is calculate the modulus. When necessary, round to the tenths place. This I do not know how to do. Can someone please explain how I should go about this? Thanks for your help.

The modulus (or absolute value) is defined as the distance from 0. For real numbers it's easy, $|-1|=1$ because it is one unit away from 0. One way you can think about the absolute value in the complex plane is the distance from 0 of the point $a+bi$ as distance between the points $(0,0)$ and $(a,b)$ by the distance formula which will yield )$|a+bi|=\sqrt{a^2+b^2}$
The modulus of a complex number $a+bi$ is defined to be $\sqrt{a^2+b^2}$. It is analogous to the length of a vector in the standard $xy$-plane.