Prove that if n is any positive integer whose last digit is a 5, then 5|n
Therefore, n is going to be 5, 15, 25, 35 etc ...
b∣a states that 'b divides a' and we know that 5∣5, 5∣15, 5∣25, 5∣35 ...
If I define my argument as, n = 5e then n/5 = e
n = 5e
5 = 5*1, 15 = 5*3, 25 = 5*5
n/5 = e
5/5 = 1, 15/5 = 3, 25/5 = 5
Is this all that is required to prove this statement as true?
You have proven that $5$, $15$, and $25$ are divisible by $5$. However, that does not cover all positive integers whose last digit is a $5$.
Hint: If the last digit of $n$ is $5$ then we can write $n = 10m+5$ for some non-negative integer $m$. Can you show that $n = 10m+5$ is divisible by $5$ no matter what integer $m$ is?