I would say 19.
If you take out the 6s and just look at the rest you have 4, 9, 14.
It is adding 5 each time and just have a 6 between each one.
So logically I would say 19.
Answer:
-21
Step-by-step explanation:
I assume this is a 2 by 2 matrix.

determinant = -5 * 4 - 1 * 1 = -20 - 1 = -21
(2,0,-1,-1,-2) that is the domain from what I remember. Hope that help