\(\dfrac{5}{2.4}+\dfrac{5}{4.6}+\dfrac{5}{6.8}+...+\dfrac{5}{48.50}\)
= \(\dfrac{2}{2}.\left(\dfrac{5}{2.4}+\dfrac{5}{4.6}+\dfrac{5}{6.8}+....+\dfrac{5}{48.50}\right)\)
\(\)\(=\dfrac{5}{2}.\left(\dfrac{2}{2.4}+\dfrac{2}{4.6}+\dfrac{2}{6.8}+....+\dfrac{2}{48.50}\right)\)
\(=\dfrac{5}{2}.\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{8}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)\)
=\(\dfrac{5}{2}.\left(\dfrac{1}{2}-\dfrac{1}{50}\right)\)
=\(\dfrac{5}{2}.\dfrac{12}{25}\)
=\(\dfrac{6}{5}\)=\(1\dfrac{1}{5}\)
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Chúc bạn làm tốt!!!
\(\dfrac{5}{2.4}+\dfrac{5}{4.6}+\dfrac{5}{6.8}+...+\dfrac{5}{48.50}\)
=\(\dfrac{5}{2}.\left(\dfrac{2}{2.4}+\dfrac{2}{4.6}+\dfrac{2}{6.8}+...+\dfrac{2}{48.50}\right)\)
=\(\dfrac{5}{2}.\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{8}+...+\dfrac{1}{48}-\dfrac{1}{50}\right)\)
=\(\dfrac{5}{2}.\left(\dfrac{1}{2}-\dfrac{1}{48}\right)\)
=\(\dfrac{5}{2}.\dfrac{23}{48}\) = \(\dfrac{115}{96}\)
\(\dfrac{5}{2.4}+\dfrac{5}{4.6}+\dfrac{5}{6.8}+...+\dfrac{5}{48.50}\)
\(=5.\left(\dfrac{1}{2.4}+\dfrac{1}{4.6}+...+\dfrac{1}{48.50}\right)\)
\(=\dfrac{5}{2}.\left(\dfrac{2}{2.4}+\dfrac{2}{4.6}+...+\dfrac{2}{48.50}\right)\)
\(=\dfrac{5}{2}.\left(\dfrac{2}{2}-\dfrac{2}{4}+\dfrac{2}{4}-\dfrac{2}{6}+...+\dfrac{2}{48}-\dfrac{2}{50}\right)\)
\(=\dfrac{5}{2}.\left(\dfrac{2}{2}-\dfrac{2}{50}\right)\)
\(=\dfrac{5}{2}.\dfrac{24}{25}\)
\(=\dfrac{12}{5}\)
=5.(1/2.4 + 1/4.6 + ....+1/48.50)
=5.[(1/2-1/4)+(1/4-1/6)+...+(1/48-1/50)]
=5.[1/2-1/4+1/4-1/6+...+1/48-1/50]
=5.[1/2-1/50]
=5.12/25
=12/5
chúc bạn học tốt!