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

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

\(\Rightarrow2x=-2.\left(-8\right)=16\)

\(\Rightarrow x=\dfrac{16}{2}=8\)

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

\(\Rightarrow-5.\left(6-5x\right)=20.\left(-14\right)\)

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

\(\Leftrightarrow25x=280-\left(-30\right)\)

\(\Rightarrow25x=310\)

\(\Rightarrow x=\dfrac{310}{25}=12,4\)

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

\(\Rightarrow x=\dfrac{119.7}{17}=49\)

\(\Rightarrow y=\dfrac{-35.17}{7}=-85\)

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

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

\(\Rightarrow\dfrac{x}{27}=\dfrac{6}{27}\)

\(\Rightarrow x=6\)

\(a:\Rightarrow x^2=\left(-2\right)\cdot\left(-8\right)=16\\ x^2=8\\ b:\Rightarrow\left(-5\right)\cdot6-5x=\left(-14\right)\cdot20=-280\\ \Rightarrow6-5x=56\\ \Rightarrow5x=6-56\\ \Rightarrow5x=-50\\ \Rightarrow x=-10\\ c:\dfrac{7}{17}=\dfrac{x}{119}\Rightarrow7\cdot119=17\cdot x=833\\ \Rightarrow x=49\\ \dfrac{49}{119}=\dfrac{-35}{y}\Rightarrow49\cdot y=119\cdot\left(-35\right)=-4165\\ \Rightarrow y=-85\\ d:\dfrac{x}{27}=\dfrac{1}{9}-\dfrac{-3}{27}\\ \dfrac{x}{27}=\dfrac{0}{27}\)