we can first simplify the numerator which is 18x^3 + 12x – 3x into 18x^3 + 9x. The simplified numerator adds the the same terms which is 12x and -3x. In this case, we can factor 9x in the numerator into 9x ( 2x2 + 1). We can cancel 3x from the numerator and the denominator. Hence the final expression results to 3 ( 2x2 + 1) / 2x.