Question

matrices question: how is the following matrix not invertible?
1 2 -1
-4 -7 3
-2 -6 4

Answer 1

Take the determinant. If the determinant is zero this matrix is not invertible. I'll try it while you do and we'll see what I get.

Answer 2

we only learned how to take the determinant of a 2 x 2 matrix... is it any more difficult?

Answer 3

ahh I see, the determinant of this matrix is zero and the pattern for taking it is similar to that for a 2x2. I'll show you: