\(D=\frac{1}{6}+\frac{1}{66}+\frac{1}{176}+\frac{1}{336}+\frac{1}{546}\)
\(D=\frac{1}{1.6}+\frac{1}{6.11}+\frac{1}{11.16}+\frac{1}{16.21}+\frac{1}{21.26}\)
\(D=\frac{1}{5}\left(\frac{5}{1.6}+\frac{5}{6.11}+\frac{5}{11.16}+\frac{5}{16.21}+\frac{5}{21.26}\right)\)
\(D=\frac{1}{5}\left(\frac{1}{1}-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+...+\frac{1}{21}-\frac{1}{26}\right)\)
\(D=\frac{1}{5}\left(\frac{1}{1}-\frac{1}{26}\right)\)
\(D=\frac{1}{5}.\frac{25}{26}=\frac{5}{26}\)
\(x+\frac{5}{3}=\frac{1}{81}\)
\(x=\frac{1}{81}-\frac{5}{3}\)
\(x=\frac{-134}{81}\)
\(x+\frac{5}{3}=\frac{1}{81}\)
\(\Leftrightarrow x=\frac{1}{81}-\frac{5}{3}\)
\(\Leftrightarrow x=-\frac{134}{81}\)
\(-52+\frac{2}{3}x=-46\)
\(\Leftrightarrow\frac{2}{3}x=-46+52\)
\(\Leftrightarrow\frac{2}{3}x=6\)
<=> 2x = 6.3
<=> 2x = 18
=> x = 9
\(\frac{x}{45}=\frac{5}{6}+\frac{-29}{30}\)
(có thể hơi khó hiểu từ bước 2, bạn lấy mẫu số chung là 30 nhé)
\(\Leftrightarrow\frac{x}{45}=\frac{25}{30}-\frac{29}{30}\)
\(\Leftrightarrow\frac{x}{45}=\frac{25-29}{30}\)
\(\Leftrightarrow\frac{x}{45}=\frac{-4}{30}\)
\(\Leftrightarrow\frac{x}{45}=\frac{-2}{15}\)
\(\Leftrightarrow x=45\left(-\frac{2}{15}\right)\)
=> x = -6
\(-52+\frac{2}{3}x=-46\)
\(\frac{2}{3}x=6\)
\(x=9\)
\(\frac{x}{45}=\frac{5}{6}+\frac{-29}{30}\)
\(\frac{x}{45}=\frac{-2}{15}\)
\(x=\frac{-2.45}{15}=-6\)
