How to multiply identity matrix with a variable?

I am unable to multiply a variable with a 16X16 identity matrix for implementing det|A-XI|. Please show me how it is done.

[John D'Errico]

A variable? A symbolic variable?

You define it as symbolic, then you use * to multiply. What is the problem? What did you try?

I would point out that almost certainly, this is going to be a bad idea, as computing a symbolic determinant of a 16x16 matrix will be very computationally nasty.

If you don't know how to multiply a variably times a matrix, this strongly suggests you need to read the getting started tutorials.