Alright, here we go:
In n/m, both are relatively prime and cannot simplify the fraction.
To prove that √3 is irrational from n^2 = 3m^2
From n^2 = 3m^2, we can say that n is a multiple of 3, since there is a 3 on the right side of the equation.
We can set n equal to 3k
So n^2 = 9k^2 = 3m^2
3k^3 = m^2
So this means that m is also a multiple of 3.
In the beginning we stated that they are relatively prime and cannot simplify, but if both are n and m are multiples of 3, how is this possible?
This leads to a contradiction.