This will generate the matrix you wantCode:with(LinearAlgebra); Matrix(3, 4, [1, 2, 3, 4, 1, k, 4, 6, 1, 1, k+2, 6]);
The first two numbers specify the size of the matrix
Then just list the element as you go though the rows!
Note loading the linear algebra package will let you use the tools from that package.
Note you can also right click on the matrix and maple will give you a list of options to choose from as well.