a) A = 20 + 21 + 22 + 23 + ... + 22010
=> 2A = 21 + 22 + 23 + ... + 22010 + 22011
=> 2A - A = (21 + 22 + 23 + ... + 22010 + 22011) - (20 + 21 + 22 + 23 + ... + 22010)
A = 21 + 22 + 23 + ... + 22010 + 22011 - 20 - 21 - 22 - 23 - ... - 22010
= 22011 - 1 = B
Vậy A = B
b) A = 2009 . 2011 = 2009 . (2010 + 1) = 2009 . 2010 + 2009
B = 20102 = 2010 . 2010 = (2009 + 1) . 2010 = 2009 . 2010 + 2010
Mà 2009 . 2010 + 2009 < 2009 . 2010 + 2010 nên A < B
c) A = 1030 = (103)10 = 100010
B = 2100 = (210)10 = 102410
Mà 102410 > 100010 A > B
d) A = 333444 = (3334)111 = [(3.111)4]111 = (34.1114)111 = (81 . 1114)111
B = 444333 = (4443)111 = [(4.111)3]111 = (43.1113)111 = (64 . 1113)111
Mà (81 . 1114)111 > (64 . 1113)111 nên A > B
e) A = 3450 = (33)150 = 27150
B = 5300 = (52)150 = 25150
Mà 27150 > 25150 nên A > B