how to plot a function that runs in m file

I have a 3x3 symbolic matrix (very large terms as functions of x) that I need to evaluate its determinant over a range of variable x. Finding determinant directly crashes so I wan to use generic equation of 3x3 matrix determinant and call in each term through a function to find the value of the determinant and then plot it. For my work I would require a very precise resolution of variable x which takes really long. Any advise?

Many thanks in advance.