Rational Roots Theorem states if a polynomial P (x) has rational roots then p/q is a root where p is a multiple of a0 and q of an. Moreover this polynomial has 3 roots, at most 3 which are positive and none of which are negative. Finding a root x0, you can use (x-x0) and long division to factor P (x) and find the other roots. Possible rational roots +/- {1,2,3,6,7,14,21}.
Namely 2,3,7 are the roots so it factors
(x-2)(x-3)(x-7)
