A=\(\frac{1}{3}\)+\(\frac{1}{8}\)+\(\frac{1}{15}\)+\(\frac{1}{24}\)+\(\frac{1}{35}\)+\(\frac{1}{48}\)+\(\frac{1}{63}\)+\(\frac{1}{80}\)

A=\(\frac{1}{2}\)(\(\frac{1}{1\cdot3}\)+\(\frac{1}{2\cdot4}\)+\(\frac{1}{3\cdot5}\)+\(\frac{1}{4.6}\)+\(\frac{1}{5.7}\)+\(\frac{1}{6.8}\)+\(\frac{1}{7.9}\)+\(\frac{2}{8.10}\))

A=\(\frac{1}{2}\)(1-1/3 +1/2-1/4 + 1/3 -1/5 +1/4-1/6 +1/5 - 1/7 +1/6 -1/8 +1/7 - 1/9 +1/8 - 1/10)

A= \(\frac{1}{2}\)(1 + 1/2 -1/9 -1/10)

A=\(\frac{29}{45}\)

\(\dfrac{1}{4}+\dfrac{1}{10}+\dfrac{1}{18}+\dfrac{1}{28}+\dfrac{1}{40}+\dfrac{1}{54}+\dfrac{1}{70}\)

\(=\left[\dfrac{1}{4}+\dfrac{1}{28}\right]+\left[\dfrac{1}{10}+\dfrac{1}{40}\right]+\left[\dfrac{1}{18}+\dfrac{1}{70}\right]\)

\(=\dfrac{2}{7}+\dfrac{6}{7}+\dfrac{1}{7}\)

\(=\dfrac{9}{7}\)

Chúc bạn học tốt nhé.

sao ko có câu hỏi và đề bài

câu hỏi ko có đề bài bạn nha

a)    \(\frac{3}{16}+\frac{4}{15}+\frac{5}{16}+\frac{1}{15}\)

\(=\left(\frac{3}{16}+\frac{5}{16}\right)+\left(\frac{4}{15}+\frac{1}{15}\right)\)

\(=\frac{1}{2}+\frac{1}{3}\)

\(=\frac{5}{6}\)

b)   \(\frac{6}{7}\times\frac{8}{15}\times\frac{7}{6}\times\frac{15}{16}\)

\(=\left(\frac{6}{7}\times\frac{7}{6}\right)\times\left(\frac{8}{15}\times\frac{15}{16}\right)\)

\(=1\times\frac{1}{2}=\frac{1}{2}\)

c)   \(\frac{19}{20}\times\frac{13}{21}+\frac{9}{20}\times\frac{8}{21}\)

\(=\frac{19\times13}{20\times21}+\frac{9\times8}{20\times21}\)

\(=\frac{247}{420}+\frac{72}{420}\)

\(=\frac{319}{420}\)

còn phần D đâu bn 

10,82896825 :V

Tổng nào bạn

cậu ghi câu hỏi ik

mik có thấy cái gì đâu

tổng gì bạn

`1/2+2/4+3/6+4/8+5/10+6/12`

`=1/2+1/2+1/2+1/2+1/2+1/2`

`=1/2*6=3`

`1/3+1/4+1/5+8/10+20/15+20/30`

`=(1/3+1/4)+(1/5+4/5)+(4/3+2/3)`

`=7/12+1+2`

`=7/12+3=43/12`

\(\dfrac{1}{2}+\dfrac{2}{4}+\dfrac{3}{6}+\dfrac{4}{8}+\dfrac{5}{10}+\dfrac{6}{12}\)
\(=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}\)
\(=\dfrac{1}{2}\times6=3\)
\(------\)
\(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{8}{10}+\dfrac{20}{15}+\dfrac{20}{30}\)
\(=\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{4}{3}+\dfrac{2}{3}\)
\(=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\dfrac{1}{4}\)
\(=\dfrac{7}{3}+1+\dfrac{1}{4}\)
\(=\dfrac{28}{12}+\dfrac{12}{12}+\dfrac{3}{12}\)
\(=\dfrac{43}{12}\)