Prove that `sqrt(n)` is not a rational number. if `n` is not a perfect square.

Explanation

Let on the contrary say it is rational .
Then
`sqrtn=p/q` `q!=0` where p and q are coprime integers.
so `n=p^2/q^2`
`p^2 =nq^2`
This shows p divides q
which is a contradiction.
Hence is irrational if n is not a perfect square.