Show that the determinant |(x+y, x , x) ( x, x+y, x) ( x ,x , x+y)| =(3x + y)y power 2

The lengths of two sides of a triangle are 9 and 15. what can be said about the length of the third side? a. it must be greater than or equal to 6 and less than 24. b. it must be greater than or equal to 6 and at most 24. c. it must be greater than 6 and less than 24. d. it must be greater than 6 and at most 24.