1. The problem statement, all variables and given/known data Consider the matrix A = 1 1 2 1 1 2 3 4 2 4 7 2t-6 2 2 6-t t Find the values of t for which the matrix A is invertible 2. Relevant equations 3. The attempt at a solution For A to be invertible, the determinant should not be 0. So what I did is find the determinant of the 4x4 matrix. Since this 4x4 matrix doesn't have any zero. I find 4 3x3 determinants which leads to 3 2x2 determinants. And a total of 12 2x2 determinants. After I sum all of them, my equation lead to 4t^2-7t+50 is not equals to zero. And I can't solve for t. This is weird because when I use online calculator for matrix, for t is 0,1,3, or any random number I put in, there is an inverse matrix.