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

Toán Lớp 7: Cho A=1+2+22+23+…+29;B=5.28. Hãy so sánhAvàB

Toán Lớp 7: Cho A=1+2+22+23+…+29;B=5.28. Hãy so sánhAvàB

Comments ( 2 )

  1. Ta có
    A=1+2+22+23+…+29
      =1+2+(22+29).8:2
      = 1+2+51.8:2
      = 3+408:2
      =3+204
      =207
    B=5.28=140
    Vậy A<B
        
     

  2.  
    Lời giải và giải thích chi tiết: 
    ${B}$ = ${5}$ .$2^{8}$ = $2^{3}$ + $2^{2}$ + ${2}$ + ${1}$ + ${1}$ + ${1}$ + ${1}$ + ${1}$ + ${1}$).$2^{6}$
    = $2^{9}$ + $2^{8}$ + $2^{7}$ + $2^{6}$ + $2^{6}$ + $2^{6}$ + $2^{6}$ + $2^{6}$ + $2^{6}$ + $2^{5}$ + $2^{5}$
    ( Vì $2^{6}$ = 2.$2^{5}$) 
    Vy B>A

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