Suppose that $a_{1}=1$ and $a_{n+1}=\frac{1}{2}\left(a_{n}+\frac{4}{a_{n}}\right) .$ Show numerically that the sequence converges to $2 .$ To find this limit analytically, $$\text { let } L=\lim _{n \rightarrow \infty} a_{n+1}=\lim _{n \rightarrow \infty} a_{n}$$ and solve the equation $$L=\frac{1}{2}\left(L+\frac{4}{L}\right)$$