proof-or-given-a-counter-example-if-p-is-prime-and-n-N-1-lt-n-p-then-pn-1-is-prime-

Question Number 475 by 123456 last updated on 25/Jan/15

p r o o f o r g i v e n a c o u n t e r e x a m p l e :

i f p i s p r i m e a n d n \in N, 1 < n ⩽ p

t h e n p n - 1 i s p r i m e

Answered by prakash jain last updated on 11/Jan/15

p = 5

n = 2

p n - 1 = 9

p is prime .

p n - 1 = 9 is not a prime .