A=2^0+2^1+2^2+....+2^100=(2^0+2^1+2^2+2^3)+(2^4+2^5+2^6+2^7)+....+(2^97+2^98+2^99+2^100)
A=2^0.(1+2+2^2+2^3)+2^4(1+2+2^2+2^3)+....+2^97(1+2+2^2+2^3)=2^0 . 15+ 2^4.15 +...+2^97 .15
A= (2^0+2^4+...+2^97)15 chia hết cho15
Vậy : A chia cho 15 dư 0
TÍCH ĐI !