Let $f ( x ) = \left( x ^ { 2 } - 2 \right) \left( x ^ { 2 } - 3 \right) \left( x ^ { 2 } - 6 \right)$. For every prime number $p$, show that $f ( x ) \equiv 0 ( \bmod p )$ has a solution in $\mathbb { Z }$.
Let $f ( x ) = \left( x ^ { 2 } - 2 \right) \left( x ^ { 2 } - 3 \right) \left( x ^ { 2 } - 6 \right)$. For every prime number $p$, show that $f ( x ) \equiv 0 ( \bmod p )$ has a solution in $\mathbb { Z }$.