Let $n$ be an integer. The number of primes which divide both $n^{2}-1$ and $(n+1)^{2}-1$ is (a) At most one. (b) Exactly one. (c) Exactly two. (d) None of the above.
(a) At most one.
Let $n$ be an integer. The number of primes which divide both $n^{2}-1$ and $(n+1)^{2}-1$ is\\
(a) At most one.\\
(b) Exactly one.\\
(c) Exactly two.\\
(d) None of the above.