Think of 16 as the sum of 64 under the root sign and 64 under the root sign, and then calculate the sum of 66 under the root sign and 62 under the root sign respectively.

) and (the sum of 64 under the root sign and 64 under the root sign).

The square of (the sum of root 66 and root 62) =66+62+2* 4092 root = 128+2 * 4092 root.

The square of (the sum of root 64 and root 64) =64+64+2, root 4096 = 128+2 *, root 4096.

So it is 16.