1）
Average=(a+b)/2
2)
Average=(a*a+b*b)^0.5

and?请补充

另外Transhumanist兄给的第二个错了吧，
应该是

((a*a+b*b)/2)的开方

更一般的

（（a的n次方+b的n次方)/2)的1/n次方。

is the name of the equation Generic Arithmetic Mean?

Refer to the follow web site for more details:
http://mathworld.wolfram.com/topics/Means.html

You are great! Could you write something on how you find information or do research on ethernet. Albeit that every guy here knows he/she may turn to google or something alike. How to utilise it and to retrieve the desirable information remains very tough.
May be your personal experience on it would help a lot to us.
Thanks.