Solve the following equations for 0<x<2pi

4cosx(cosx-1)=-5cosx

i managed to do-

4cos^2(x) - 4cosx = -5cosx

4cos^2(x) + cosx = 0

4cosx + 1 = 0

cosx = -1/4

x = 104.5

I used the cos graph but the answers I was given were-

x= 90, -90, 104, -104

bit confused