\(A=\left(2^1+2^2+2^3+2^4\right)+....+\left(2^{97}+2^{98}+2^{99}+2^{100}\right)+1\)
\(=2.15+2^5.15+...+2^{97}.15+1=15.\left(2+2^5+...+2^{97}\right)+1\)
A 15 dư 1
\(A=\left(1+2+2^2+2^3\right)+\left(2^4+2^5+2^6+2^7\right)+...+\left(2^{97}+2^{98}+2^{99}+2^{100}\right)\)
\(=15+2^4.\left(1+2+2^2+2^3\right)+...+2^{97}.\left(1+2+2^2+2^3\right)\)
\(=15+2^4.15+...+2^{97}.15\)
\(=15.\left(1+2^4+...+2^{97}\right)\text{chia hết cho 15}\)
=> A chia hết cho 15
=> A chia 15 dư 0.
Là 0 bạn nhé vì:
2.(1+2+2^2+2^3) + 2^5.(1+2+2^2+2^3) + ... 2^95.(1+2+2^2+2^3)
=2.15 + 2^5.15 + ... + 2^95 . 15
=(2 + 2^5 + ... 2^95) . 15
=> A chia hết cho 15.