Đáp án:
2^3.S = 2#.(1 – 2^3 + 2^6 – 2^9+ . . . + 2^96 – 2^99)
8S = 2^3 – 2^6 + 2^9 – 2^12+ . . . + 2^99 – 2^102
8S + S = (2^3 – 2^6+ 2^9 – 21^12+ . . . + 2^99 – 2^102)+(1 – 2^3 + 2^6 – 2^9+ . . . + 2^96 – 2^99)
=>9S=1-2^102
=>S=1-2^102:9
Xin hay nhất ạ!!!