Answer
$3x^2+4x^5$
Work Step by Step
Recall the following rule: $\frac{a^{m}}{a^{n}}=a^{m-n}$
In order to solve this problem, use the rule above and cancel out common factors that are in both the numerator and the denominator of the fraction.
$=\dfrac{12x^3}{4x} + \dfrac{16x^6}{4x}
\\=3x^{3-1} +4x^{6-1}
\\=3x^2+4x^5$
