Register Now

Login

Lost Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

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

Toán Lớp 6: Cho A= 2 + 2^2 + 2^3 + 2^4 + –… + 2^100 Chứng minh A chia hết cho 3 giúp mình vói khó wá

Toán Lớp 6: Cho A= 2 + 2^2 + 2^3 + 2^4 + ……….. + 2^100
Chứng minh A chia hết cho 3
giúp mình vói khó wá

Comments ( 2 )

  1. $\begin{array}{l} A= 2 +2^2+2^3+2^4 + … +2^{100} \\ \to A = (2+2^2) + (2^3+2^4) + … + (2^{97} + 2^{98}) +(2^{99}+2^{100}) \\ \to A = 2(1+2) + 2^3(1+2) + … + 2^{97}(1+2) +2^{99}(1+2) \\  \to A = 2 . 3 + 2^3 .3 + … +2^{97} . 3 +2^{99} . 3 \\ \to A = 3(2+2^3+ .. +2^{97} +2^{99} )  \\ \text{Vì } 3 \vdots 3 \Rightarrow A = 3(2+2^3+ .. +2^{97} +2^{99} ) \vdots 3 \end{array}$

  2. Lời giải và giải thích chi tiết:
    -Ta có: A = 2+2^2+2^3+2^4+……+2^100
    => A = (2+2^2)+(2^3+2^4)+……..+(2^99+2^100)
    => A=2.(1+2)+2^3 . (1+2) +………+ 2^99 . (1+2)
    => A = 3 . (2+2^3+……….+2^99) vdots 3
    => A vdots 3 (đpcm) 

Leave a reply

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