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

Toán Lớp 7: 1+1/5+1/5^2+1/5^3+-.+1/5^500 giúp tôi

Toán Lớp 7: 1+1/5+1/5^2+1/5^3+…..+1/5^500
giúp tôi

Comments ( 2 )

  1. Giải đáp+Lời giải và giải thích chi tiết:
    Đặt ,A=1+1/5+1/5^2+1/5^3+. . . ..+1/5^500$\\$=>5A=5+1+1/5+1/5^2+…..+1/5^499$\\$=>5A-A=(5+1/5^499)-1/5^500$\\$=>4A=5-1/5^500$\\$=>A=[5-1/5^500]/4

  2. Đặt A = 1 + 1/5 + 1/5^2 + 1/5^3 + …. + 1/5^500
    5A = 5 + 1 + 1/5 + 1/5^2 + …. + 1/5^499
    5A – A = ( 5 + 1 + 1/5 + 1/5^2 + …. + 1/5^499 ) – ( 1 + 1/5 + 1/5^2 + 1/5^3 + …. + 1/5^500 )
    4A = 5 – 1/5^500
    4A = ( 5^501 – 1 )/5^500
    A = ( 5^501 – 1 )/5^500 : 4
    A = ( 5^101 – 1 )/( 5^500 . 4 )
    Vậy , A = ( 5^101 – 1 )/( 5^500 . 4 ) .

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