lam ho 1)A) 1- (5va4/9 +X -7va 7/18): 15va3/4=0
; B)X +1/2+1/4+1/8+1/16+1/32+1/64+1/128
---------------------------------------------------------- =9/2
1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9
2)
a)A=
5+8/17 +8/37
------------------
4+4/17+4/37
B)B=7/12+7/6+7/12+...+7/9900
B = 1 + 2 + 4 + 8 + ...+1024+ 2048
=> 2 x B = 2 + 4 + 8 + 16 + ...+ 2048 + 4096
=> 2 x B - B = 4096 - 1
B = 4096 - 1
B = 4095
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