Source : <https://www.youtube.com/watch?v=tAfLEocGgDs&list=PLDE28CF08BD313B2A&index=16>

* In his college algebra video lessons ( #26) , Pr. R. Delaware states that :

> 
> a real polynomial function of degree $n$ has $n$ real or complex roots
>  ***counting multiplicities***
> 
> 
> 

* I think I understand what is the multiplicity of a root : when a root appears in a linear factor ( once the polynomial has been factored) the multiplicity of the root is the exponent of the factor.
* What I don't understand clearly is in which way not counting multiplicities produces ( or can produce) a false result as to the number of roots.
* Could you please provide an example showing the importance of counting multiplicities?