\(d,\left(1-\dfrac{4}{7}\right)\left(\dfrac{-3}{8}-\dfrac{-5}{7}\right)=\dfrac{3}{7}.\dfrac{19}{56}=\dfrac{57}{392}\\ e,\left(-\dfrac{5}{6}\right)^2=\dfrac{25}{36}\\ c,\dfrac{4}{3}-\dfrac{1}{3}:5+\dfrac{3}{4}=\dfrac{4}{3}-\dfrac{1}{15}+\dfrac{3}{4}=\dfrac{19}{15}+\dfrac{3}{4}=\dfrac{121}{60}\)

Lời giải:
a.

$\frac{x}{-2}=\frac{-8}{x}$

$\Rightarrow x^2=(-2)(-8)=16=4^2=(-4)^2$

$\Rightarrow x=4$ hoặc $x=-4$

b.

$\frac{-5}{-14}=\frac{20}{6-5x}$

$\frac{5}{14}=\frac{20}{6-5x}$

$\Rightarrow 6-5x=20.14:5=56$

$x=-10$

c: 7/17=x/119=-35/y

\(\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{119\cdot7}{17}=49\\y=\dfrac{-35\cdot17}{7}=-85\end{matrix}\right.\)

d: =>x/27-1/9=1/9

=>x/27=2/9

=>x=6

a: \(=\dfrac{3}{11}+\dfrac{18}{66}=\dfrac{18}{66}+\dfrac{18}{66}=\dfrac{36}{66}=\dfrac{6}{11}\)

b: \(=\dfrac{2}{9}-\dfrac{5}{12}+\dfrac{3}{4}\)

\(=\dfrac{8}{36}-\dfrac{15}{36}+\dfrac{27}{36}=\dfrac{20}{36}=\dfrac{5}{9}\)

c: \(=\dfrac{3\cdot7-5}{35}\cdot\dfrac{-40-30}{16}\)

\(=\dfrac{16}{35}\cdot\dfrac{-70}{16}=-2\)

d: \(=\dfrac{1}{5}\cdot\dfrac{2-7}{4}-\dfrac{3}{4}\cdot\dfrac{4-11}{12}\)

\(=\dfrac{1}{5}\cdot\dfrac{-5}{4}-\dfrac{3}{4}\cdot\dfrac{-7}{12}\)

\(=\dfrac{-1}{4}+\dfrac{21}{48}=\dfrac{-12+21}{48}=\dfrac{9}{48}=\dfrac{3}{16}\)

a: \(\Leftrightarrow x^2=16\)

hay \(x\in\left\{4;-4\right\}\)

b: \(\Leftrightarrow\dfrac{20}{6-5x}=\dfrac{5}{14}\)

=>6-5x=56

=>5x=-50

hay x=-10

c: =>7/17=x/119=-35/y

=>x=49; y=-85

d: =>x/27=1/9+1/9=2/9

hay x=6

\(a,\dfrac{x}{-2}=\dfrac{-8}{x}\)

\(\Leftrightarrow x^2=16\Rightarrow\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

\(b,\dfrac{5}{14}=\dfrac{20}{6-5x}\)

\(\Leftrightarrow30-25x=280\)

\(\Leftrightarrow25x=30-280=-250\)

\(\Leftrightarrow x=-10\)

\(c,\dfrac{7}{17}=\dfrac{x}{119}=\dfrac{-35}{y}\)

\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{119.7}{17}=49\\y=\dfrac{-35.17}{7}=-85\end{matrix}\right.\)

\(d,\dfrac{x}{27}+\dfrac{-3}{27}=\dfrac{1}{9}\)

\(\dfrac{x-3}{27}=\dfrac{1}{9}\)

\(9x-27=27\)

\(9x=54\Rightarrow x=6\)

a)\(\dfrac{x}{-2}=-\dfrac{8}{x}\)

\(\Rightarrow x^2=16\)

\(\Rightarrow x=-4\) hoặc x=4

b)\(-\dfrac{5}{-14}=\dfrac{20}{6-5x}\)

\(\Rightarrow-5\left(6-5x\right)=-280\)

\(-30+25x=-280\)

25x=-250

x=-10

c)\(\dfrac{7}{17}=\dfrac{x}{119}=-\dfrac{35}{y}\)

\(\Rightarrow\dfrac{x}{119}=\dfrac{7}{17}\Rightarrow x=49\)

     \(-\dfrac{35}{y}=\dfrac{7}{17}\Rightarrow y=-85\)

d)\(\dfrac{x}{27}+\dfrac{-3}{27}=\dfrac{1}{9}\)

\(\dfrac{x-3}{27}=\dfrac{1}{9}\)

\(x-3=3\)

x=6

\(a,\dfrac{8}{35}\)

\(b,\dfrac{15}{8}\)

\(c,\dfrac{30}{21}\)

\(d,\dfrac{72}{175}\)

de qha

A.8/35

B.15/8

C.30/21

D.72/175

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25/9-2=25/9-18/9=7/9

4-5/7=28/7-2/7=26/7

189/45-2=189/45-90/45=99/45

6-1515/1818=6-15/18=6-5/6=36/6-5/6=31/6

\(25^2:100^0=\left(5^2\right)^2:1=5^4\\ 30^3:30^0=2^3.3^3.5^3:1=2^3.3^3.5^3\)