MS =   + + + +   = TS 2 3 4 20121 1 1 1 1 1 1 1+ + + + + + + +

2012 ... 2012.

MS =   + + + +   = TS

 

2 3 4 2012

1 1 1 1 1 1 1 1

+ + + + + + + +

... ... 1

2 3 4 2012 2 3 4 2012

= = =

Khi đó :

A

 

2011 2010 2009 ... 1 2012 1 1 ... 1 2012

+ + + +   + + +  

1 2 3 2011 2 3 2012

1 1 1 1 1

+ + + + +

2 3 4 ... 99 100