Answer
$9x^6-12x^4-15x^2$
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.
$=\dfrac{27x^7}{3x} - \dfrac{36x^5}{3x}- \dfrac{45x^3}{3x}
\\=9x^{7-1}- 12x^{5-1}-15x^{3-1}
\\=9x^6-12x^4-15x^2$
