By inspection, -1 is a root of f(x). Divide f(x) synthetically by x+1 to get:
f(x) = (x+1)(x4-5x3+9x2+x-14)
-1 is also a root of the second factor. Divide that factor synthetically be x+1 to obtain:
f(x) = (x+1)2(x3-6x2+15x-14)
2 is a root of x3-6x2+15x-14. Dividing synthetically by x-2, we have:
f(x) = (x+1)2(x-2)(x2-4x+7)
Use the quadratic formula to find the remaining roots. They are 2±√3i.