Answer
Error $=(n-8)^2$
Correct solution $=(n+8)(n-8)$
Work Step by Step
The given polynomial is
$= n^2-64$
Write the polynomial as $a^2-b^2$.
$= n^2-8^2$
Use difference of two square pattern
$a^2-b^2=(a+b)(a-b)$.
We have $a=n$ and $b=8$.
$= (n+8)(n-8)$
Hence, the error is $(n-8)^2$ and the correct solution is $(n+8)(n-8)$.