Bài 12: Phép chia phân số

\(A=\left(1-\dfrac{1}{10}\right):\left(1+\dfrac{1}{10}\right):\left(1+\dfrac{1}{11}\right):\left(1+\dfrac{1}{12}\right):...:\left(1+\dfrac{1}{500}\right)\)
\(=\dfrac{9}{10}:\dfrac{11}{10}:\dfrac{12}{11}:\dfrac{13}{12}:...:\dfrac{501}{500}\)
\(=\dfrac{9}{10}\cdot\dfrac{10}{11}\cdot\dfrac{11}{12}\cdot\dfrac{12}{13}\cdot....\cdot\dfrac{500}{501}\)
\(=\dfrac{9}{501}=\dfrac{3}{167}\)

\(3\cdot\left(\dfrac{1}{2}-x\right)-5\left(x-\dfrac{1}{10}\right)=-\dfrac{7}{4}\\ \Leftrightarrow-8x=-\dfrac{15}{4}\\ \Leftrightarrow x=\dfrac{15}{32}\)

\(4\left(\dfrac{3}{4}+x\right)-\dfrac{1}{5}=7x-\dfrac{1}{7}\\ \Leftrightarrow3x=\dfrac{103}{35}\\ \Leftrightarrow x=\dfrac{103}{105}\)

\(3\left(\dfrac{1}{2}-x\right)-5\left(x-\dfrac{1}{10}\right)=-\dfrac{7}{4}\)

\(\Rightarrow\dfrac{3}{2}-3x-5x+\dfrac{1}{2}=-\dfrac{7}{4}\)

\(\Rightarrow2-8x=-\dfrac{7}{4}\)

\(\Rightarrow8x=2+\dfrac{7}{4}\)

\(\Rightarrow8x=\dfrac{15}{4}\)

\(\Rightarrow x=\dfrac{15}{32}\)

___________

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

\(\Rightarrow3+4x-\dfrac{1}{5}=7x-\dfrac{1}{7}\)

\(\Rightarrow4x+\dfrac{14}{5}=7x-\dfrac{1}{7}\)

\(\Rightarrow7x-4x=\dfrac{14}{5}+\dfrac{1}{7}\)

\(\Rightarrow3x=\dfrac{103}{35}\)

\(\Rightarrow x=\dfrac{103}{105}\)

`3(1/2 - x) - 5(x -1/10) = -7/4`

`=> 3/2 - 3x - 5x + 1/2 = -7/4`

`=> (-3x- 5x) + (3/2 + 1/2) = -7/4`

`=> -8x + 2 = -7/4`

`=>   -8x     = -15/4`

`=>      x     = 15/32`

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

`=> 3 + 4x - 1/5 = 7x - 1/7`

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

`=> 4x + 14/5     = 7x - 1/7`

`=> 4x - 7x         = -14/5 - 1/7`

`=> -3x              = -103/35`

`=>    x              = 103/105`

`5/2 -3(1/3-x)=1/4-7x`

`=> 5/2 - 1 + 3x=1/4 -7x`

`=>3x+7x= 1/4 - 5/2 +1`

`=> 10x= 1/4 - 10/4 +4/4`

`=>10x= -5/4`

`=>x=-5/4 :10`

`=>x=-5/4 xx1/10`

`=>x= -5/40=-1/8`

=>5/2-3+3x=1/4-7x

=>10x=1/4-5/2+3=3/4

=>x=3/40

a: \(A=\dfrac{2}{15}+\dfrac{13}{15}-\dfrac{1}{4}-\dfrac{3}{4}+\dfrac{1}{2}=\dfrac{1}{2}\)

b: =5,4(-3,6-6,4)

=5,4*(-10)

=-54

1000000000:10=100000000

1 000 000 000 : 10= 100 000 000

100000000

( -3/4 ?1/6)

Dấu nào vậy bạn

`(-3/4 + 1/6) : (5/9 - 1/6)`

`= ( -18/24 + 4/24) : ( 30/54 - 9/54)`

`= -14/24 : 21/54`

`= -7/12 : 7/18`

`= -7/12 xx 18/7`

`= -3/2`

(-3/4+1/6):(5/9-1/6)

=\(\dfrac{-7}{12}\):\(\dfrac{7}{18}\)

=\(\dfrac{-3}{2}\)

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chiếm bao nhiêu em, chỗ đó bị lỗi rồi

a)\(-5,3;-2,99;-2,9;0,3;0,7;25\)

b)\(25;0,7;0,3;-2,9;-2,99;-5,3\)

a,-5,3;-2,99;-2,9;0,7;25,03.

b,25,03;0,7;-2,9;-2,99;-5,3.

\(\dfrac{4}{5}+\dfrac{7}{3}\div x=\dfrac{1}{6}\)

        \(\dfrac{7}{3}\div x=\dfrac{1}{6}-\dfrac{4}{5}\)

        \(\dfrac{7}{3}\div x=-\dfrac{19}{30}\)

               \(x=\dfrac{7}{3}\div\left(-\dfrac{19}{30}\right)\)

               \(x=-\dfrac{70}{19}\)

\(a)\left(-\dfrac{3}{4}\div\dfrac{2}{-3}\right)\times\dfrac{-5}{7}\)

 \(=\dfrac{9}{8}\times\dfrac{-5}{7}\)

\(=\dfrac{-45}{56}\)

\(b)\dfrac{-2}{-5}\div\left(\dfrac{7}{-5}\div\dfrac{-3}{2}\right)\)

\(=\dfrac{2}{5}\div\left(\dfrac{7}{-5}\div\dfrac{-3}{2}\right)\)

\(=\dfrac{2}{5}\div\dfrac{14}{15}\)

\(=\dfrac{3}{7}\)