Đáp án:
S= 2+$2^{3}$+ $2^{5}$+....+$2^{99}$
S= (2+$2^{3}$+$2^{5}$+$2^{7}$)+($2^{9}$+$2^{11}$+$2^{13}$+$2^{15}$)+....+($2^{93}$+$2^{95}$+$2^{97}$+$2^{99}$)
S=2(1+$2^{2}$+$2^{4}$+$2^{6}$)+$2^{9}$(1+$2^{2}$+$2^{4}$+$2^{6}$)+...+$2^{93}$(1+$2^{2}$+$2^{4}$+$2^{6}$)
S=2.170+$2^{9}$+170+...+$2^{93}$ .170
S=170(2+$2^{9}$+...+$2^{93}$ chia hết cho 10 (Đpcm)