(6) The sequence {an} is defined by a1 = 1 and a_{n+1}=\left(2 a_{n}+1\right)^{\frac{1}{2}}-\frac{1}{4}\left(2 a_{n}+1\right)^{\frac{1}{4}}, \quad n=1,2, \ldots Show that the sequence is convergent.