It a 3x3 matrix with the top being [2, 2, -1], the middle [-4, -8, 6], and the bottom being [-13+k, 10, -9] I'm just using the commas to show that the numbers are not together in one vector. The question is find k such that the matrix M is singular.
[ 2 2 -1]
[ -4 -8 6]
[-13+k 10 -9]
[ 2 2 -1]
[ -4 -8 6]
[-13+k 10 -9]