Ta có :
\(8^7-2^{18}=\left(2^3\right)^7-2^{18}\)
\(=2^{21}-2^{18}\)
\(=2^{18}\left(2^3-1\right)\)
\(=2^{18}.7\)
\(=2^{17}.2.7\)
\(=2^{17}.14⋮14\)
Vậy \(8^7-2^{18}⋮14\rightarrowđpcm\)
Ta có:
\(8^7-2^{18}=\left(2^3\right)^7-2^{18}\)
\(=2^{21}-2^{18}=2^{18}.\left(2^3-1\right)\)
\(=2^{17}.2.7=2^{17}.14\)
Vì \(14⋮14\) nên \(2^{17}.14⋮14\)
=> \(8^7-2^{18}⋮14\) (đpcm)
Chúc bạn học tốt!!!
Giải:
\(8^7-2^{18}\)
\(=\left(2^3\right)^7-2^{18}\)
\(=2^{21}-2^{18}\)
\(=2^{18}.\left(2^3-1\right)\)
\(=2^{18}.\left(8-1\right)\)
\(=2^{18}.7\)
\(=2^{17}.2.7\)
\(=2^{17}.14⋮14\) (đpcm)
Chúc bạn học tốt!
87-218=221-218=218(23-1)=218.7=14.217 chia hết cho 14 nha
Ta có: 87-218
nên: (23)7-218
=221-218
=218.23-218.1
=218(23-1)
=218(8-1)
=218-7
=217.2.7
=(217.14)\(⋮\)14(14\(⋮\)14)
Vậy 87-218 chia hết 14
