Hi I'm trying to work out this question - its in the matrices section. Any help would be appreciated! thanks.

2. Determine the values of x for which the system of equations below has a non-trivial solution:

xc1 + c2 + c3 + c4 = 0

c1 + xc2 + c4 = 0

c1 + xc3 + c4 = 0

c1 + c2 + c3 + xc4 = 0