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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 5: tính nhanh : 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 = ????

Toán Lớp 5: tính nhanh : 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 = ????

Comments ( 1 )

  1. $ A = 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 $ 
    $ 2A = 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 $ 
    $ 2A – A = ( 1 + 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 ) – ( 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128 + 1/256 ) $
    $ A = 1 – 1/256 = 256/256 – 1/256=255/256 $
     

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222-9+11+12:2*14+14 = ? ( )