2A:
a: \(\dfrac{x}{20}=\dfrac{1.5}{6}\)
=>\(\dfrac{x}{20}=\dfrac{1}{4}\)
=>\(x=\dfrac{20}{4}=5\)
b: ĐKXĐ: x<>0
\(\dfrac{-9}{x}=\dfrac{x}{-4}\)
=>\(x^2=\left(-9\right)\cdot\left(-4\right)=36\)
=>\(\left[{}\begin{matrix}x=6\left(nhận\right)\\x=-6\left(nhận\right)\end{matrix}\right.\)
2B:
b: \(\dfrac{x}{2,6}=\dfrac{-8}{3,9}\)
=>\(x=2.6\cdot\dfrac{-8}{3.9}=\dfrac{2}{3}\cdot\left(-8\right)=-\dfrac{16}{3}\)
b: ĐKXĐ: x<>0
\(\dfrac{25}{x}=\dfrac{x}{4}\)
=>\(x\cdot x=25\cdot4\)
=>\(x^2=100\)
=>\(\left[{}\begin{matrix}x=10\left(nhận\right)\\x=-10\left(nhận\right)\end{matrix}\right.\)
`2A.`
`a,` `x/20 = (1,5)/6`
`=> x . 6 = 1,5 . 20`
`=> x .6 = 30`
`=> x = 5`
`b,` `(-9)/x = x/(-4)`
`=> x^2 = (-9) . (-4)`
`=> x^2 = 36`
`=> x= +-6`
``
`2B`
`a,` `x/(2,6) = (-8)/(3,9)`
`=> x . 3,9 = (-8) . 2,6`
`=> x . 3,9 = -20,8`
`=> x = -16/3`
`b,` `25/x = x/4`
`=> x^2 = 25.4`
`=> x^2 = 100`
`=> x = +-10`
