Easy -1.2 This is a 1-mark multiple choice question requiring students to test four small values by computing 2^n ± 1 and checking primality of single-digit or two-digit numbers. It's purely computational with no problem-solving or insight required, making it easier than average.
Dan believes that
for every positive integer \(n\), at least one of \(2^n - 1\) and \(2^n + 1\) is prime.
Which value of \(n\) shown below is a counter example to Dan's belief?
Circle your answer.
[1 mark]
\(n = 3\) \(n = 4\) \(n = 5\) \(n = 6\)
Dan believes that
for every positive integer $n$, at least one of $2^n - 1$ and $2^n + 1$ is prime.
Which value of $n$ shown below is a counter example to Dan's belief?
Circle your answer.
[1 mark]
$n = 3$ $n = 4$ $n = 5$ $n = 6$
\hfill \mbox{\textit{AQA AS Paper 1 2019 Q2 [1]}}