By "reduce" you mean factor into factors having integer coefficients. The "rational root theorem" will help here. It says that any rational roots of the equation must be of the form x= k/m where m is a factor of and k is a factor of . The only factors of -1 are 1 and -1 and the only factors of 16 are 1, -1, 2, -2, 4, -4, 8, -8, 16, and -16. The means that the only possible rational roots must be 1, -1, 2, -2, 4, -4, 8, -8, 16, or -16. Put each of those into to see if they make it 0. If none of them do then there are no rational roots and this cannot be factored with integer coefficients. If one does work, divide by (x- that root) to find the other factor.