Can anyone please help a novice?

I am trying to acquire eigenvalues from a matrix over a range of values of "k" and then plot the eigenvalue points on a graph. Can any one help with the code? Especially for the do loop and plotting the graph.

Here is my matrix:

C:=linalg[matrix](2, 2, [9*(1-k), 4*k, -4*k, 2*(1-k)]);