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![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có A + 1 = 1 + 3 + 32 + 33 + 34 + 35 + ... + 32019 + 32020 + 32021
= (1 + 3 + 32) + (33 + 34 + 35) + ... + (32019 + 32020 + 32021)
= (1 + 3 + 32) + 33(1 + 3 + 32) + ... + 32019(1 + 3 + 32)
= (1 + 3 + 32)(1 + 33 + ... + 32019)
= 13(1 + 33 + ... + 32019) \(⋮\)13
=> A : 13 dư 12
\(A=3+3^2+3^3+...+3^{2021}\)
\(A=\left(3+3^2+3^3\right)+\left(3^4+3^5+3^6\right)+...+\left(3^{2019}+3^{2020}+3^{2021}\right)\)
\(A=3\left(1+3+3^2\right)+3^4\left(1+3+3^2\right)+...+3^{2019}\left(1+3+3^2\right)\)
\(A=3.13+3^4.13+...+3^{2019}.13\)
\(A=13\left(3+3^4+...+3^{2019}\right)\)
\(\Rightarrow A⋮13\)
Hay \(A:13\)k dư
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có :
\(x\left(-2\right)^4=\left(-2\right)^7\)
\(x=\left(-2\right)^7:\left(-2\right)^4\)
\(x=\left(-2\right)^3\)
Vậỵ chọn C
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)