I'm experiencing difficulties trying to find the eigenvalues of the follow matrix. The hint is to use an elementary row operation to simplify

but I can't think of a suitable one to use or figure out whether a single row operation will actually make the calculations simpler.
Out of desperation, and having seen it being done once(not sure if it is correct) I decided to then subtract the first column from the second column.
I'm not even sure if subtracting columns from each other was a valid step. I know that subtracting rows is but I'm not sure about columns. I'm just wondering if that step was correct because if it is then I can get the eigenvalues from it fairly easily.