Multiplying polynomials in Mathematica

[SMA_01]

I have two polynomials

(1+x+x^2+x^3) and (1+x+x^2+x^3+x^4), I'm trying to figure out how to compute the product in Mathematica, but it's not working.

Any help is appreciated, thanks.

 

[Daniiel]

Expand[(1+x+x^2+x^3)*(1+x+x^2+x^3+x^4)]