Solve for Cos(x), be sure to check for All Options that are possible (You only need to solve for Cos x, not x)
6cos^2x+17cosx=-5
Let x = cos x then substitute
6 x^2 +17 x = -5
6x^2 +17x +5=0 Use quadratic formula to find x = -1/3
cos x = -1/3 (?)