... Bài 1.8 : Cho 22 22 91 4131 2 1++++=A. Chứng minh 985 2 << A Bài 1.9 : Cho 22 22 2007 2 7 2 5 2 3 2 ++++=A. Chứng minh: 20 081003<A Bài 1.10 : Cho 22 22 20061 816141++++=B. ... 9171697137791316931333:854 28 9474485 12 289 12 7 12 12 ++++++−−−−−−=KBµi 4.11: TÝnh 20 .1516. 121 2.98.64.310.58.46.34 .22 .1++++++++=L13Bµi 4. 12: TÝnh 5 2 :5,0.6,017 2 2.41 2 95574: 25 2 08,1 25 164,0 25 ,1.531:6,1+−−+−=MBµi ... ] 22 2)1( 12 )3 .2( 5 )2. 1(3+++++nnnTa có : [ ];)1(11)1( 12 222 +=++iiiii i = 1 ; 2 ; 3; ; nDo đó Sn = ( 1- ++++ 22 222 )1(11 31 2 1) 2 1nn = 1- 22 )1( )2( )1(1++=+...