let us take contradiction that 3√2 is rational number.
so if 3√2 is a rational number then
let 3√2=a/b,where a and b are co primes
here in the R.H.S side
that is a/3b is a rational number but in the L.H.S side √2 is irratioanal
so 3√2 is a irrational number..................hope it helped u:))))))