need help using polyval and finding roots

p is the value that was entered for the input, I have to make p into a row vector with at most 7 terms.

First I have to assume p contains the coefficients of a polynomial and plot the polynomial using 1000 points in the domain [-5,5], Then I need to determine the roots of the polynomial and mark it on my plot if inside the domain. I'm stuck at getting p into a row vector with a number of terms in it, in the latter part i know im supposed to use polyval but I cant even get the vector