The geometric mean of 3 and 6 is
3•6= 18
Sqrt (18)= sqrt (2•3•3)= 3 sqrt (2)
If you have to find the geometric mean of two numbers like 3 and 6,
think that 3 by 6 will give you a rectangle and the geometric mean will give you a square 3 sqrt (2) by 3 sqrt (3)