1/2 x 1/3 x 1/7 + 1/2 x 1/3 x 2/7 + 1/2 x 1/3 x 4/7
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\(B=\dfrac{1+\dfrac{1}{7}+\dfrac{1}{7^2}-\dfrac{1}{7^3}}{4+\dfrac{4}{7}+\dfrac{4}{7^2}-\dfrac{4}{7^3}}\cdot\dfrac{858585}{313131}\cdot\left(-1\dfrac{14}{17}\right)\)
\(=\dfrac{1}{4}\cdot\dfrac{85}{31}\cdot\dfrac{-31}{17}\)
\(=\dfrac{-5}{4}\)
a: =8/15x1/4=2/15
b: \(=\dfrac{5}{3}\cdot\dfrac{4}{5}\cdot\dfrac{6}{7}=\dfrac{24}{21}=\dfrac{8}{7}\)
c: \(=\dfrac{2}{5}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\)
\(\frac{1}{2}\cdot\frac{18}{14}+\frac{1}{2}\cdot\frac{3}{14}-\frac{1}{2}\cdot\frac{7}{14}\)
\(=\frac{1}{2}\left(\frac{18}{14}+\frac{3}{14}-\frac{7}{14}\right)\)
\(=\frac{1}{2}\cdot1=\frac{1}{2}\)
1/2 x 1/3 x 1/7 + 1/2 x 1/3 x 2/7 + 1/2 x 1/3 x 4/7
= 1/2 x 1/3 x (1/7 + 2/7 + 4/7)
= 1/6 x 1
= 1/6
\(\dfrac{1}{2}\times\dfrac{1}{3}\times\dfrac{1}{7}+\dfrac{1}{2}\times\dfrac{1}{3}\times\dfrac{2}{7}+\dfrac{1}{2}\times\dfrac{1}{3}\times\dfrac{4}{7}\)
\(=\dfrac{1}{2}\times\dfrac{1}{3}\times\left(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{4}{7}\right)\)
\(=\dfrac{1}{2}\times\dfrac{1}{3}\times1=\dfrac{1}{6}\)