(a^4)(³√a(a^5))
Hopefully that makes sense.
Do you mean $\displaystyle a^4 \cdot \sqrt[3]{a(a^5)}$ or $\displaystyle a^4 \cdot \sqrt[3]{a} \cdot a^5$
You would do well to recall the exponent laws, namely the one that says $\displaystyle m^n \cdot m^p = m^{n+p}$ and the one that says $\displaystyle \sqrt[n]{m} = m^{1/n}$