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![](https://rs.olm.vn/images/avt/0.png?1311)
\(P=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9+2^{10}\)
\(P=2\left[\left(1+2+2^2+2^3+2^4\right)+\left(2^5+2^6+2^7+2^8+2^9\right)\right]\)
\(P=2\left[\left(1+2+2^2+2^3+2^4\right)+2^5\left(1+2+2^2+2^3+2^4\right)\right]\)
\(P=2\left(2^5+1\right)\left(1+2+2^2+2^3+2^4\right)\)
Mà: \(1+2+2^2+2^3+2^4=31\Rightarrow P⋮31\left(đpcm\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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\(6+6^2+\cdot\cdot\cdot+6^{10}\)
\(=6\cdot\left(1+6\right)+6^3\cdot\left(1+6\right)+\cdot\cdot\cdot+6^9\cdot\left(1+6\right)\)
\(=6\cdot7+6^3\cdot7+\cdot\cdot\cdot+6^9\cdot7\)
\(=7\cdot\left(6+6^3+\cdot\cdot\cdot+6^9\right)⋮7\)
\(\Rightarrow6+6^2+\cdot\cdot\cdot\cdot+6^{10}⋮7\)
![](https://rs.olm.vn/images/avt/0.png?1311)
A=(2+22)+(23+24)+...+(29+210)
=2(1+2)+23(1+2)+...+29(1+2)
=2.3+23.3+...+29.3
=3.(2+23+...+29) luôn chia hết cho 3
Có: A = ( 2 + 22 + 23 + 24 + 25 ) + ( 26 + 27 + 28 + 29 + 210 )
còn lại tự lm