**Solution :**

Let us assume that 3+2√3 is rational .

So, x= 3+2√3

x^{2}=(3+2√3)^{2 }

x^{2}=21+12√3

√3=(x^{2}−21)/12…….(1)

because x is a rational number

So, the expression (x^{2}−21)/12 is also a rational number.This is a contradiction .Hence, 3+2√3 is irrational .