Hi all, this is my first post

Could somebody point in the right direction for solving this question.

I have a 2X2 matrix A

-50 -8

336 54

i am asked to find in terms of m, the expression det(A-mI)

and show it as a quadratic expression

[IMG]file:///C:/Users/IANDUG%7E1/AppData/Local/Temp/moz-screenshot.png[/IMG]

Where do i start? I am probably missing something really obvious

All help appreciated

Ian999