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

Toán Lớp 6: Giúp em với ạ. Em cảm ơn. n+(n+1)+(n+2)+(n+3)-.+(n+9)= 20255

Toán Lớp 6: Giúp em với ạ. Em cảm ơn.
n+(n+1)+(n+2)+(n+3)…..+(n+9)= 20255

Comments ( 2 )

  1. n + (n + 1) + (n + 2) + (n + 3) + …. + (n + 9) = 20255
    => n + n + 1 + n + 2 + …. + n + 9 = 20255
    => (n + n + …. + n) + (1 + 2 + ….. + 9) = 20255
    => 10n + 45 = 20255
    => 10n = 20255 – 45
    => 10n = 20210
    => n = 20210 : 10
    => n = 2021
    Vậy n = 2021

  2. n+(n+1)+(n+2)+(n+3)+. . .+(n+9)=20255
    n+n+1+n+2+n+3+. . .+n+9=20255
    (n+n+. . .+n)+(1+2+. . .+9)=20255
    10 xx n + 45 = 20255
    10 xx n = 20255-45
    10 xx n = 20210
    n = 20210 : 10
    n = 2021

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