\(S=\frac{1}{8}+\frac{1}{24}+\frac{1}{48}+...+\frac{1}{224}\)
\(S=\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+...+\frac{1}{14.16}\)
\(2S=\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+...+\frac{2}{14.16}\)
\(2S=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{14}-\frac{1}{16}\)
\(2S=\frac{1}{2}-\frac{1}{16}\)
\(S=\frac{7}{16}:2=\frac{7}{32}\)
Ủng hộ mk nha !!! ^_^
\(S=\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+...+\frac{1}{14.16}\)
\(S=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{14}-\frac{1}{16}\)
\(S=\frac{1}{2}-\frac{1}{16}\)
\(S=\frac{7}{16}\)
\(S=\frac{1}{8}+\frac{1}{24}+...+\frac{1}{224}\)
\(\Rightarrow\frac{1}{2.4}+\frac{1}{4.6}+...+\frac{1}{14.16}\)
\(\Rightarrow\frac{1}{2}\left(\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{14.16}\right)\)
\(\Rightarrow\frac{1}{2}\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{14}-\frac{1}{16}\right)\)
\(\Rightarrow\frac{1}{2}\left(1-\frac{1}{16}\right)\)
\(\Rightarrow\frac{1}{2}.\frac{15}{16}\)\(\Rightarrow S=\frac{15}{32}\)
\(S=\frac{1}{8}+\frac{1}{24}+\frac{1}{48}+....+\frac{1}{224}\)
\(=\frac{1}{2.4}+\frac{1}{4.6}+....+\frac{1}{14.16}\)
\(=\frac{1}{2}\left(\frac{2}{2.4}+....+\frac{2}{14.16}\right)\)
\(=\frac{1}{2}\left(1-\frac{1}{4}+\frac{1}{4}-......+\frac{1}{14}-\frac{1}{16}\right)\)
\(=\frac{1}{2}\left(1-\frac{1}{16}\right)\)
\(=\frac{7}{32}\)
\(S=\frac{1}{8}+\frac{1}{24}+\frac{1}{48}+....+\frac{1}{224}\)
\(S=\frac{1}{2\cdot4}+\frac{1}{4\cdot6}+\frac{1}{6\cdot8}+.....+\frac{1}{14\cdot16}\)
\(2S=\frac{2}{2\cdot4}+\frac{2}{4\cdot6}+\frac{2}{6\cdot8}+.....+\frac{2}{14\cdot16}\)
\(2S=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+.....+\frac{1}{14}-\frac{1}{16}\)
\(2S=1-\frac{1}{16}\)
\(S=\frac{15}{16}:2\)
\(S=\frac{15}{32}\)
