The Attempt at a Solution
Do you see where it says 3.3(1-lambda)?
Then the next row has -9 in it? It should be -9 + 9lambda, right? I'm using the Sars method (I think that's what it's called), where you copy the first two columns then take the product of three different diagonals, then subtract them from 3 other diagonals, sorry for the vague language.