`S_1 = 5/(1.4) + 5/(4.7) +...+ 5/(97.100)`

`S_1 = 5 (1/(1.4) + 1/(4.7) +...+ 1/(97.100))`

`S_1 = 5/3 (3/(1.4) + 3/(4.7) +...+ 3/(97.100))`

`S_1 = 5/3 (1 - 1/4 + 1/4 - 1/7 + ...+ 1/97 - 1/100)`

`S_1 = 5/3 (1 - 1/100)`

`S_1 = 5/3 . 99/100`

`S_1 = 33/20`

\(\dfrac{-1}{9}.\dfrac{-3}{5}+\dfrac{5}{-6}.\dfrac{-3}{5}-\dfrac{7}{2}.\dfrac{3}{5}\)

\(=\dfrac{3}{5}.\left(\dfrac{1}{9}+\dfrac{5}{6}-\dfrac{7}{2}\right)\)

\(=\dfrac{3}{5}.\left(\dfrac{2}{18}+\dfrac{15}{18}-\dfrac{63}{18}\right)\)

\(=\dfrac{3}{5}.\left(-\dfrac{23}{9}\right)\)

\(=-\dfrac{69}{45}\)

\(-\dfrac{5}{7}\times\dfrac{2}{13}+\dfrac{-5}{7}\times\dfrac{3}{13}-\dfrac{5}{7}\times\dfrac{8}{13}\)

\(=-\dfrac{5}{7}\left(\dfrac{2}{13}+\dfrac{3}{13}+\dfrac{8}{13}\right)\)

\(=-\dfrac{5}{7}\times\dfrac{13}{13}\)

\(=-\dfrac{5}{7}\times1=-\dfrac{5}{7}\)

\(-\dfrac{5}{7}.\dfrac{2}{13}+\dfrac{-5}{7}.\dfrac{3}{13}-\dfrac{5}{7}.\dfrac{8}{13}\)

\(=-\dfrac{10}{91}-\dfrac{15}{91}-\dfrac{40}{91}\)

\(=\dfrac{-10-15-40}{91}\)

\(=-\dfrac{65}{91}=-\dfrac{5}{7}\)

\(\dfrac{-5}{7}.\dfrac{2}{13}+\left(\dfrac{-5}{7}\right).\dfrac{3}{13}-\dfrac{5}{7}.\dfrac{8}{13}\)

\(=\dfrac{5}{7}.\left(\dfrac{-2}{13}+\dfrac{-3}{13}-\dfrac{8}{13}\right)\)

\(=\dfrac{5}{7}.\left(-1\right)\)

\(=-\dfrac{5}{7}\)

\(#PaooNqoccc\)

`(-12)/(9-x) =4/5`

`=> -12.5=(9-x).4`

`=> -60=(9-x).4`

`=> (9-x).4=-60`

`=>9-x=-60:4`

`=>9-x=-15`

`=>x=9-(-15)`

`=>x=9+15`

`=>x= 24`

`5/9+4/9:x=1/3`

`=>4/9:x=1/3-5/9`

`=>4/9:x=3/9-5/9`

`=>4/9:x=-2/9`

`=>x=4/9:(-2/9)`

`=>x=4/9.(-9/2)`

`=>x=-4/2`

`=>x=-2`

`5/9 + 4/9 : x= 1/3`

`=> 4/9 : x= 1/3-5/9`

`=> 4/9 : x= 3/9-5/9`

`=> 4/9 : x= -2/9`

`=> x= 4/9 :(-2/9)`

`=>x= 4/9 xx (-9/2)`

`=>x= -36/18`

`=>x=-2`

5/9+4/9:x=1/3 

          1:x=1/3

             x= 1: 1/3

             x= 3 

Theo tui là thế vì có mỗi phép cộng làm cộng trước xong đó tính x là ra nếu thấy cách làm thế nào thì mn bình luộn nha 

`1/5 . 4/7 + 3/7 . 1/5 -1/5`

`=1/5 . 4/7 + 3/7 . 1/5 -1/5 . 1`

`=1/5 . ( 4/7+3/7-1)`

`=1/5 . ( 7/7-1)`

`= 1/5 . 0`

`=0`

\(\dfrac{1}{5}\times\dfrac{4}{7}+\dfrac{3}{7}\times\dfrac{1}{5}-\dfrac{1}{5}=\dfrac{1}{5}\times\left(\dfrac{4}{7}+\dfrac{3}{7}-1\right)=\dfrac{1}{5}\times0=0\)

= \(\dfrac{1}{5}\).(\(\dfrac{4}{7}\)+\(\dfrac{3}{7}\)+1)

= \(\dfrac{1}{5}\)+ 0

\(\dfrac{1}{5}\)

1<4/x<=-5/8

mà 1>-5/8

nên \(x\in\varnothing\)

a: \(=\dfrac{-39+19+10}{12}=\dfrac{-10}{12}=\dfrac{-5}{6}\)

b: \(=\dfrac{2^{30}\cdot3^{16}\cdot7-2^{34}\cdot3^{15}}{2^{28}\cdot3^{21}-2^{28}\cdot3^{17}}\)

\(=\dfrac{2^{30}\cdot3^{15}\left(3\cdot7-2^4\right)}{2^{28}\cdot3^{17}\left(3^4-1\right)}=\dfrac{2^2}{3^2}\cdot\dfrac{21-16}{80}=\dfrac{4}{9}\cdot\dfrac{5}{80}\)

\(=\dfrac{20}{720}=\dfrac{1}{36}\)

MSC : `840`

`-5/8=-5.105/8.105=-525/840`

`7/10=7.84/10.84=588/840`

`-16/14=-16.60/14.60=-960/840`

`23/24=23.35/24.35=805/840`

`-1=-840/840`

Sắp xếp các phân số sau theo thứ tự giảm dần:

`805/840;588/840;-525/840;-840;-960/840`