Ta có :
\(3^{15}+3^{16}+3^{17}\)
\(=3^{15}\cdot\left(1+3+3^2\right)=3^{15}\cdot13⋮13\)
\(\rightarrow3^{15}+3^{16}+3^{17}⋮13\left(đpcm\right)\)
Ta có : \(3^{15}+3^{16}+3^{17}\)
\(=3^{15}\cdot\left(1+3+3^2\right)=3^{15}\cdot13⋮13\)
\(\Rightarrow3^{15}+3^{16}+3^{17}⋮13\)(đpcm)
\(3^{15}+3^{16}+3^{17}=3^{15}\left(1+3+3^2\right)=3^{15}.13⋮13\)
Bài làm :
Ta có :
\(3^{15}+3^{16}+3^{17}\)
\(=3^{15}\left(1+3+3^2\right)\)
\(=3^{15}.13⋮13\)
=> Điều phải chứng minh
315 + 316 + 317
= 315( 1 + 3 + 32 )
= 315.13 chia hết cho 13 ( đpcm )
