All complex numbers come in two parts: the real and the imaginary ones. That's why we can write all complex numbers as
![a+bi](https://img.qammunity.org/2021/formulas/mathematics/high-school/21g05dswb8vv8mx498tmsymwz0ibzmxpy4.png)
where
is the real coefficient, and
is the imaginary coefficient.
In particular, you can see that, if you set
, you have the usual real numbers again. For example, choose
and
to get
![5+0i=5](https://img.qammunity.org/2021/formulas/mathematics/college/ks6i5lqvzmmkr9gscsdaov521jv0owttn2.png)
So, real numbers are actually already complex numbers, just like you can think of integers as fraction, where
![5=(5)/(1)](https://img.qammunity.org/2021/formulas/mathematics/college/fil2ho8rbn1me9u9tsw63putief9ngs0jo.png)