If (7)n end with the digit 5, then the number should be divisible by 5.
This means the prime factorization of 7n should contain prime factor 5.
But (7)n does not have the prime factor 5. So, the uniqueness of the Fundamental Theorem of Arithmetic guarantees that there are no other primes in the factorization of 7n.
, 5 is not present in the prime factorization, there is no natural number nor which 7n ends with digit 5.
So, 7n cannot end with digit 5.
Rate this question :