Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 11 - Sequences; Induction; the Binomial Theorem - Section 11.4 Mathematical Induction - 11.4 Assess Your Understanding - Page 850: 28

Answer

When $n=1$, the value of $n^2-n+41$ is $41$, which is a prime number. However when $n=41$, the value of $n^2-n+41$ is $41$ is $4162$, which is not prime. Thus, the statement :$``n^2 - n + 41\text{ is a prime number"}$ is not true.

Work Step by Step

We need to prove that $p(n): n^2-n+41$ is a prime number. Let us check for $n=1$ that $p(1)$ is true. So, we have: $n^2-n+41=1-1+41=41$, this shows that $p(1)$ is a true and $41$ is prime. Let us check for $n=41$ that $p(41)$ is true. So, we have: $n^2-n+41=41^2-41+41=(41)^2$, this shows that $p(41)$ is not true and $(41)^2$ is not prime. (because it has $41$ as a factor apart from $1$ and itself. Thus, the statement $p(n): n^2-n+41$ is not true.
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