Use the Definition of Big- $O$ To Prove That $1 ^ { 2 } + 2 ^ { 2 } + \cdots + n ^ { 2 }$

Short Answer

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