S=1+2+23+...+29
\(\Rightarrow2S=2+2^2+....+2^{10}\)
\(\Rightarrow2S-S=\left(2+2^2+...+2^{10}\right)\)-(1+2+22+...+29)
\(\Rightarrow S=2+2^2+...2^{10^{ }}-1-2-2^2-....-2^9\)
S=210-1
ta có (4+1).28=4.28+28=28.28+28=210+28
\(\Rightarrow2^{10}-1< 2^{10^{ }}+2^{8^{ }}hayS< 5.2^8\)
Ta có S=1+2+23+...+29
=>2S=2(1+2+23+...+29)
=>2S=2+23+...+210
=>2S-S=(2+23+...+210)-(1+2+23+...+29)
=>S=210-1
Mà 5.28=4.2x8+2x8=2x10+2x8
=>210-1<2x10+2x8
Hay S<5.28