Question

show that 3√2 is irrational

Answer 1

let 3√2 is rational
3√2=p/q
√2=p/3q
since a irrational number cannot be equal to rational number
3√2 is irrational.

Answer 2

contd.
when a rational number is multiplied with an irrational number the result is always irrational
here 3 is a rational number it is multiplied to root 2 which is irrational (already proved).
so are 3 into root 2 is 3 root 2 which is irrational (proved.)