CHỨNG MINH A=2 MŨ 2020 +4 MŨ 1011+8 MŨ 675 CHIA HẾT CHO 37
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\(A=3^{2022}-2^{2022}+3^{2020}-2^{2020}\\=(3^{2022}+3^{2020})-(2^{2022}+2^{2020})\\=3^{2020}\cdot(3^2+1)-2^{2020}\cdot(2^2+1)\\=3^{2020}\cdot10-2^{2019}\cdot2\cdot5\\=3^{2020}\cdot10-2^{2019}\cdot10\)
Ta có: \(\left\{{}\begin{matrix}3^{2020}\cdot10⋮10\\2^{2019}\cdot10⋮10\end{matrix}\right.\)
\(\Rightarrow3^{2020}\cdot10-2^{2019}\cdot10⋮10\)
hay \(A⋮10\) (đpcm)
\(\text{#}Toru\)
a, 942^60-351^37
=(942^4)^15-351^37
=(....6)^15 -351^37
suy ra( 942^4)^15 có tận cùng là 6
357^37 có tận cùng là 1
hiệu của 942^60-351^37 có tận cùng là 5
suy ra 942^60-351^37 chia hết cho 5
a) Ta có: 942^60=(942^4)^15=...6^15=...6
351^37=...1
Suy ra: 942^60-351^37=...5 chia hết cho 5. Vậy 942^60-351^37 chia hết cho 5
b) Làm tương tự câu trên
*Ta có: A\(=2^1+2^2+2^3+2^4+...+2^{2010}\)
\(=\left(2+2^2\right)+2^2\times\left(2+2^2\right)+...+2^{2008}\times\left(2+2^2\right)\)
\(=\left(2+2^2\right)\times\left(1+2^2+2^3+...+2^{2008}\right)\)
\(=6\times\left(2^2+2^3+...+2^{2008}\right)\)
\(=3\times2\times\left(2^2+2^3+...+2^{2008}\right)\)
\(\Rightarrow A⋮3\)
*Ta có: A \(=2^1+2^2+2^3+2^4+...+2^{2010}\)
\(=2\times\left(1+2+2^2\right)+2^4\times\left(1+2+2^2\right)+...+2^{2008}\times\left(1+2+2^2\right)\)
\(=\left(1+2+2^2\right)\times\left(2+2^4+2^7+...+2^{2008}\right)\)
\(=7\times\left(2+2^4+2^7+...+2^{2008}\right)\)
\(\Rightarrow A⋮7\)
Mình sửa lại đề C 1 chút xíu
*Ta có: C \(=3^1+3^2+3^3+3^4+...+3^{2010}\)
\(=\left(3+3^2\right)+3^2\times\left(3+3^2\right)+...+3^{2008}\times\left(3+3^2\right)\)
\(=\left(3+3^2\right)\times\left(1+3^2+3^3+...+3^{2008}\right)\)
\(=12\times\left(1+3^2+3^3+...+3^{2008}\right)\)
\(=4\times3\times\left(1+3^2+3^3+...+3^{2008}\right)\)
\(\Rightarrow C⋮4\)
Các câu khác làm tương tự nhé. Chúc bạn học tốt!
a) \(A=2^1+2^2+2^3+2^4+...+2^{2010}\)
\(A=\left(2^1+2^2\right)+\left(2^3+2^4\right)+...+\left(2^{2009}+2^{2010}\right)\)
\(A=2\left(1+2\right)+2^3\left(1+2\right)+...+2^{2009}\left(1+2\right)\)
\(A=3\left(2+2^3+...+2^{2009}\right)⋮3\)
\(A=2^1+2^2+2^3+2^4+...+2^{2010}\)
\(A=\left(2^1+2^2+2^3\right)+\left(2^4+2^5+2^6\right)+...+\left(2^{2008}+2^{2009}+2^{2010}\right)\)
\(A=2\left(1+2+2^2\right)+2^4\left(1+2+2^2\right)+...+2^{2008}\left(1+2+2^2\right)\)
\(A=7\left(2^1+2^4+...+2^{2008}\right)⋮7\)
Các ý dưới bạn làm tương tự nhé.
A=(1+3+32)+(33+34+35)+...+(32019+32020+32021) A=(1+3+32)+33.(1+3+32)+...+32019.(1+3+32)
A=13+33.13+...+32019.13
A=13.(1+33+...+32019)chia hết cho 13
=>A chia hết cho 13
a, \(S=3^0+3^2+3^4+3^6+...+3^{2020}\)
\(\Leftrightarrow3^2S=3^2+3^4+3^6+3^8+...+3^{2022}\)
\(\Leftrightarrow3^2S-S=3^{2022}-3^0\)
\(\Leftrightarrow9S-S=3^{2022}-1\)
\(\Leftrightarrow8S=3^{2022}-1\Leftrightarrow S=\frac{3^{2022}-1}{8}\)
b,\(S=3^0+3^2+3^4+3^6+...+3^{2020}\)
\(=\left(3^0+3^2+3^4\right)+\left(3^6+3^8+3^{10}\right)+...+\left(3^{2016}+3^{2018}+3^{2020}\right)\)
\(=\left(1+3^2+3^4\right)+3^6\left(1+3^2+3^4\right)+...+3^{2016}\left(1+3^2+3^4\right)\)
\(=\left(1+3^2+3^4\right)\left(1+3^6+...+3^{2016}\right)\)
\(=91\left(1+3^6+...+3^{2016}\right)=13.7\left(1+3^6+...+3^{2016}\right)⋮7\)
=> đpcm
Tham khảo :
a, S=30+32+34+36+...+32020
⇔32S=32+34+36+38+...+32022
⇔32S−S=32022−30
⇔9S−S=32022−1
⇔8S=32022−1⇔S=32022−18
b,S=30+32+34+36+...+32020
=(30+32+34)+(36+38+310)+...+(32016+32018+32020)
=(1+32+34)+36(1+32+34)+...+32016(1+32+34)
=(1+32+34)(1+36+...+32016)
=91(1+36+...+32016)=13.7(1+36+...+32016)⋮7 (
=> (đpcm)
=>99