Use the Definition of Big- $O$ To Prove That $\frac { 3 n - 8 - 4 n ^ { 3 } } { 2 n - 1 }$

Use the definition of big- $O$ to prove that $\frac { 3 n - 8 - 4 n ^ { 3 } } { 2 n - 1 }$ is $O \left( n ^ { 2 } \right)$