Trang chủ » Hỏi đáp » Môn Toán Cho A = 2 + 2^2 + 2^3 + 2^4 + … + 2^20 CMR A chia hết cho 3 07/05/2024 Cho A = 2 + 2^2 + 2^3 + 2^4 + … + 2^20 CMR A chia hết cho 3
A=2+2^2+2^3+2^4+…+2^20 = (2+2^2)+(2^3+2^4)+…+(2^19+2^20) = (2+2^2)+2^2(2+2^2)+..+2^18(2+2^2) = (2+2^2)(1+2^2+..2^18) = 6(1+2^2+..+2^18) Có: 6 vdots 3 => 6(1+2^2+…2^28) vdots 3 Vậy 2+2^2+2^3+2^4+…+2^20 vdots 3 Trả lời
A = 2 + 2^2 + 2^3 + 2^4 + … + 2^20 A = (2 +2^2) + (2^3+2^4) + …. + (2^19+2^20) A = (2+2^2) + 2^2(2+2^2) + … + 2^18(2 + 2^2) A = (2+2^2).(1+2^2+…+2^18) A = 6.(1+2^2+…+2^18)\vdots 3 ->A\vdots 3 $\color{red}{\text{@Hy~Hoctotnha}}$ Trả lời
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