To sum up, whether or not we admit that the Counter-thesis √2=p/q (p and q are relative primes)can be false, The condition of “that the original proposition is true if the counterproposition is false”cannot be satisfied, so the method of contradiction cannot be applied.Therefore, √2=p/q (p and q are relative primes) is not the inverse proposition of "√ 2 is not a rational number". In other words, the inverse proposition of √2=p/q (p and q are relative primes) is not a rational number can only be √2=p/q (p and q are both integers).