Toán Tìm dư của phép chia A cho 7 biết : A=2+2^2+2^3+2^4+………+2^1000 09/10/2021 By Ayla Tìm dư của phép chia A cho 7 biết : A=2+2^2+2^3+2^4+………+2^1000
$A=2+2^2+2^3+2^4+………+2^{1000}$ $=(2+2^2+2^3)+(2^4+2^5+2^6+2^7)+………+(2^{997}+2^{998}+2^{999}+2^{1000})$ $=2(1+2+2^2)+2^4(1+2+2^2)+…+2^{997}(1+2+2^2)$ $=2.7+2^4.7+…+2^{997}.7$ $=7.(2+2^4+…+2^{997}$ ⋮ $7$ Vậy $A$ ⋮ $7$. Trả lời
$A=2+2^2+2^3+2^4+………+2^{1000}$
$=(2+2^2+2^3)+(2^4+2^5+2^6+2^7)+………+(2^{997}+2^{998}+2^{999}+2^{1000})$
$=2(1+2+2^2)+2^4(1+2+2^2)+…+2^{997}(1+2+2^2)$
$=2.7+2^4.7+…+2^{997}.7$
$=7.(2+2^4+…+2^{997}$ ⋮ $7$
Vậy $A$ ⋮ $7$.