Question

 Tìm x, biết:

Answer 1

`a, 6/5 + 4/5 : x = 3/4`

`4/5 : x = -9/20`

`=> x = -16/9`

`b, (5x + 2/3)^2 = 4/9`

`=>` \(\left[ \begin{array}{l}5x+2/3=2/3\\5x+2/3=-2/3\end{array} \right.\) 

`=>` \(\left[ \begin{array}{l}x=1/5\\x=-4/15\end{array} \right.\) 

Answer 2

a)`1 1/5 + 4/5 :x =0,75`

`4/5:x = 0,75 - 1 1/5`

`4/5:x= 3/4 -6/5 = 15/20 - 24/20 = -9/20`

`=> x = 4/5 : (-9/20) = -16/9`

b)\(3.\left(5x+\dfrac{2}{3}\right)^2=\dfrac{4}{3}\)

\(\Rightarrow\left(5x+\dfrac{2}{3}\right)^2=\dfrac{4}{9}\)

\(\Rightarrow\left[{}\begin{matrix}5x+\dfrac{2}{3}=\dfrac{2}{3}\\5x+\dfrac{2}{3}=-\dfrac{2}{3}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}5x=0\\5x=-\dfrac{4}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{4}{15}\end{matrix}\right.\)

Answer 3

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Answer 4

\(1\dfrac{1}{5}+\dfrac{4}{5}:x=0.75\)

`6/5 + 4/5 : x = 0,75`

`4/5 : x = 0.75 - 6/5`

`4/5 : x = 3/4 - 6/5`

`4/5 : x = (-9)/20`

`x = 4/5 : (-9)/20`

`x = 4/5 xx 20/(-9)`

`x= (-16)/9`

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` 3.(5x + 2/3)^2 = 4/3`

`(5x + 2/3)^2 = 4/3 : 3`

`(5x + 2/3)^2 = 4/3 xx 1/3`

`(5x + 2/3)^2 = 4/9`

`(5 + 2/3)^2 = (2/3)^2`

`TH1)`

` 5x + 2/3 = 2/3`

`5x = 2/3 - 2/3`

`5x = 0`

`x= 0 : 5`

`x = 0`

`TH2`)

`5x + 2/3 = - 2/3`

`5x = -2/3 - 2/3`

`5x = -4/3`

`x = -4/3 : 5`

`x = -4/15`

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Answer 5

\(a,1\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\\ \Rightarrow\dfrac{6}{5}+\dfrac{4}{5}:x=\dfrac{3}{4}\\ \Rightarrow\dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{6}{5}\\ \Rightarrow\dfrac{4}{5}:x=-\dfrac{9}{20}\\ \Rightarrow x=-\dfrac{16}{9}\)

\(b,3\left(5x+\dfrac{2}{3}\right)^2=\dfrac{4}{3}\\ \Rightarrow\left(5x+\dfrac{2}{3}\right)^2=\dfrac{4}{9}\\ \Rightarrow\left(5x+\dfrac{2}{3}\right)^2=\left(\pm\dfrac{2}{3}\right)^2\\ \Rightarrow\left[{}\begin{matrix}5x+\dfrac{2}{3}=\dfrac{2}{3}\\5x+\dfrac{2}{3}=-\dfrac{2}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{4}{15}\end{matrix}\right.\)

Answer 6

`a) 1 1/5 + 4/5 : x = 0,75`

`=> 6/5 + 4/5 : x    = 3/4`

`=>           4/5 : x    = 3/4 - 6/5`

`=>            4/5 : x   = -9/20`

`=>                    x    = 4/5 : -9/20`

`=>                     x    = -16/9`

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`b) 3(5x + 2/3)^2 = 4/3`

`=>  (5x + 2/3)^2  = 4/3 : 3`

`=>   (5x + 2/3)^2  = 4/9`

`=>`\(\left\{{}\begin{matrix}\left(5x+\dfrac{2}{3}\right)^2=\left(\dfrac{2}{3}\right)^2\\\left(5x+\dfrac{2}{3}\right)^2=\left(-\dfrac{2}{3}\right)^2\end{matrix}\right.\)

`=>`\(\left\{{}\begin{matrix}5x+\dfrac{2}{3}=\dfrac{2}{3}\\5x+\dfrac{2}{3}=-\dfrac{2}{3}\end{matrix}\right.\)

`=>`\(\left\{{}\begin{matrix}5x=\dfrac{2}{3}-\dfrac{2}{3}\\5x=-\dfrac{2}{3}-\dfrac{2}{3}\end{matrix}\right.\)

`=>`\(\left\{{}\begin{matrix}5x=0\\5x=-\dfrac{4}{3}\end{matrix}\right.\)

`=>`\(\left\{{}\begin{matrix}x=0:5\\x=-\dfrac{4}{3}:5\end{matrix}\right.\)

`=>`\(\left\{{}\begin{matrix}x=0\\x=-\dfrac{4}{15}\end{matrix}\right.\)

Answer 7

a/ \(\Leftrightarrow\dfrac{4}{5}:x=0,75-1\dfrac{1}{5}\)

\(\Leftrightarrow\dfrac{4}{5}:x=-\dfrac{9}{20}\)

\(\Leftrightarrow x=\dfrac{4}{5}:\left(-\dfrac{9}{20}\right)\)

\(\Leftrightarrow x=\dfrac{4}{5}.\dfrac{-20}{9}\)

\(\Leftrightarrow x=-\dfrac{16}{9}\)

Vậy x = ...

b/\(\Leftrightarrow\left(5x+\dfrac{2}{3}\right)^2=\dfrac{4}{9}\)

\(\Leftrightarrow25x^2+\dfrac{20}{3}x+\dfrac{4}{9}=\dfrac{4}{9}\)

\(\Leftrightarrow x\left(25x+\dfrac{20}{3}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{4}{15}\end{matrix}\right.\)

Vậy x= ...