Violympic toán 7

LM

\(\dfrac{3}{2}+\dfrac{13}{6}+\dfrac{37}{12}+\dfrac{81}{20}+\dfrac{151}{30}+\dfrac{253}{42}+\dfrac{393}{56}+\dfrac{577}{72}+\dfrac{811}{90}\)

TT
11 tháng 11 2017 lúc 19:47

\(\dfrac{3}{2}+\dfrac{13}{6}+\dfrac{37}{12}+\dfrac{81}{20}+\dfrac{151}{30}+\dfrac{253}{42}+\dfrac{393}{56}+\dfrac{577}{72}+\dfrac{811}{90}\)

\(=\dfrac{459}{10}\)

Bình luận (2)
QH
11 tháng 11 2017 lúc 19:55

\(\dfrac{3}{2}+\dfrac{13}{6}+\dfrac{37}{12}+\dfrac{81}{20}+\dfrac{151}{30}+\dfrac{253}{42}+\dfrac{393}{56}+\dfrac{577}{72}+\dfrac{811}{90}\)\(=\dfrac{2}{2}+\dfrac{1}{2}+\dfrac{12}{6}+\dfrac{1}{6}+\dfrac{36}{12}+\dfrac{1}{12}+\dfrac{80}{20}+\dfrac{1}{20}+\dfrac{150}{30}+\dfrac{1}{30}+\dfrac{252}{42}+\dfrac{1}{42}+\dfrac{392}{56}+\dfrac{1}{56}+\dfrac{576}{72}+\dfrac{1}{72}+\dfrac{810}{90}+\dfrac{1}{90}\)\(=1+\dfrac{1}{2}+2+\dfrac{1}{6}+3+\dfrac{1}{12}+4+\dfrac{1}{20}+5+\dfrac{1}{30}+6+\dfrac{1}{42}+7+\dfrac{1}{56}+8+\dfrac{1}{72}+9+\dfrac{1}{90}\)\(=\left(1+2+3+4+5+6+7+8+9\right)+\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}\right)\)= 45 + \(\dfrac{9}{10}\)

= \(\dfrac{459}{10}\)

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NC
11 tháng 11 2017 lúc 20:05

\(\dfrac{3}{2}+\dfrac{13}{6}+\dfrac{37}{12}+\dfrac{81}{20}+\dfrac{151}{30}+\dfrac{253}{42}+\dfrac{393}{56}+\dfrac{393}{56}+\dfrac{577}{72}+\dfrac{811}{90}\)

\(\dfrac{3780+5460+7770+10206+12684+15180+17685+20195+22708}{2520}\)=\(\dfrac{115668}{2520}=\dfrac{459}{10}\)

Bình luận (0)

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