how to create a matrix with variables in it?

for eg., to create following matrix and work on it,

A=[x1 x1*x2 ; x1^2 x2^2]

Answer 1

[Kye Taylor]

The best answer to your question will likely depend on what you want to do with A. Sometimes, I find the following commands useful, which will create an anonymous function, A, that takes two inputs, x1 and x2 and returns the matrix you describe. Of course, this assumes you have values for the variables x1 and x2.

A = @(x1,x2)[x1,x1*x2;x1^2,x2^2]

And compute, for example, with

det(A(1,2))

If you want A to be symbolic, you can begin using the following command

syms x1 x2
A = [x1,x1*x2;x1^2,x2^2]

Then compute, for example, with

det(A)

Answer 2

[Aman Kumar]

syms x1 x2

A = [x1,x1*x2;x1^2,x2^2]

[Michael Wolfe]

How would you make a matrix with both numbers and variables in it?

[Walter Roberson]

syms x1 x2
A = [x1,x1*pi;.8,x2^2]