Answer
$10a^{3}+12a^{2}+9a-20$
Work Step by Step
$\left[\begin{array}{lllllllll}
& 2a^{2} & +4a & +5 & & & & & \\
& & 5a & -4 & & & & & \\
-- & -- & -- & -- & & & & & \\
& -8a^{2} & -16a & -20 & \text{multiply by }-4 & & & & \\
10a^{3} & +20a^{2} & +25a & & \text{multiply by } 5a & & & & \\
-- & -- & -- & -- & \text{add like terms } & & & & \\
10a^{3} & +12a^{2} & 9a & -20 & & & & &
\end{array}\right.$
Answer: $10a^{3}+12a^{2}+9a-20$
