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a: \(\dfrac{x}{0.9}=\dfrac{5}{6}\)
\(\Leftrightarrow x=\dfrac{3}{4}\)
b: \(\dfrac{-6}{x}=\dfrac{9}{-15}\)
\(\Leftrightarrow x=10\)
c: \(\dfrac{\dfrac{14}{15}}{\dfrac{9}{10}}=\dfrac{x}{\dfrac{3}{7}}\)
\(\Leftrightarrow x=\dfrac{3}{7}\cdot\dfrac{14}{15}:\dfrac{9}{10}=\dfrac{2}{5}\cdot\dfrac{10}{9}=\dfrac{20}{45}=\dfrac{4}{9}\)
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b: \(\left[\left(6+\dfrac{3}{5}-3-\dfrac{3}{14}\right)\cdot\dfrac{2}{5}\right]:\left(21-1.25\right)=x:\left(5+\dfrac{5}{6}\right)\)
\(\Leftrightarrow x:\dfrac{35}{6}=\dfrac{237}{175}:\dfrac{79}{4}\)
\(\Leftrightarrow x:\dfrac{35}{6}=\dfrac{12}{175}\)
\(\Leftrightarrow x=\dfrac{2}{5}\)
a) \(\frac{14}{15}:\frac{9}{10}=x:\frac{3}{7}\)
=> \(\frac{28}{27}=x:\frac{3}{7}\)
=> \(x=\frac{28}{27}.\frac{3}{7}\)
=> \(x=\frac{4}{9}\)
Vậy \(x=\frac{4}{9}.\)
b) \(1\frac{3}{5}:8=2,5:x\)
=> \(\frac{8}{5}:8=\frac{5}{2}:x\)
=> \(\frac{1}{5}=\frac{5}{2}:x\)
=> \(x=\frac{5}{2}:\frac{1}{5}\)
=> \(x=\frac{25}{2}\)
Vậy \(x=\frac{25}{2}.\)
Chúc bạn học tốt!
3.
a) \(\left|x\right|=2,1\Leftrightarrow\left[\begin{array}{nghiempt}x=2,1\\x=-2,1\end{array}\right.\)
b)\(\left|x\right|=\frac{17}{9}\Leftrightarrow x=-\frac{17}{9}\) (vì x/<0)
c) \(\left|x\right|=1\frac{2}{5}\Leftrightarrow\left|x\right|=\frac{7}{5}\Leftrightarrow\left[\begin{array}{nghiempt}x=\frac{7}{5}\\x=-\frac{7}{5}\end{array}\right.\)
d) \(\left|x\right|=0,35\Leftrightarrow x=0,35\) (Vì x>0)
2.
a) \(\left|x-1,7\right|=2,3\)
\(\Leftrightarrow\begin{cases}x\ge1,7\\x-1,7=2,3\end{cases}\) hoặc \(\begin{cases}x< 1,7\\1,7-x=2,3\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge1,7\\x=4\left(tm\right)\end{cases}\) hoặc \(\begin{cases}x< 1,7\\x=-0,6\left(tm\right)\end{cases}\)
Vậy x={4;-0,6}
b) đề thiếu
a) |- 2,5| = 2,5 b) |- 2,5| = - 2,5 c) |- 2,5| = - |- 2,5|
>.<
\(\left(-\frac{28}{19}\right)\times\left(-\frac{38}{14}\right)=\frac{14\times2\times19\times2}{19\times14}=4\)
>.<
\(\left(-\frac{21}{16}\right)\times\left(-\frac{24}{7}\right)=\frac{7\times3\times8\times3}{8\times2\times7}=\frac{9}{2}\)
>.<
\(\left(-\frac{12}{17}\right)\times\left(-\frac{34}{9}\right)=\frac{3\times4\times17\times2}{17\times3\times3}=\frac{8}{3}\)
>.<
\(\left|x\right|=2,1\)
\(x=\pm2,1\)
>.<
\(\left|x\right|=\frac{17}{9}\)
\(x=\pm\frac{17}{9}\)
x < 0
\(x=-\frac{17}{9}\)
>.<
\(\left|x\right|=1^2_5\)
\(x=\pm\frac{7}{5}\)
>.<
\(\left|x\right|=0,35\)
\(x=\pm0,35\)
x > 0
x = 0,35
>.<
\(\left|x-1,7\right|=2,3\)
\(x-1,7=\pm2,3\)
Th1:
x - 1,7 = 2,3
x = 2,3 + 1,7
x = 4
Th2:
x - 1,7 = - 2,3
x = - 2,3 + 1,7
x = - 0,6
>.<
\(\left|x+\frac{3}{4}\right|-\frac{1}{3}=0\)
\(\left|x+\frac{3}{4}\right|=\frac{1}{3}\)
\(x+\frac{3}{4}=\pm\frac{1}{3}\)
Th1:
x + 3/4 = 1/3
x = 1/3 - 3/4
x = \(-\frac{5}{12}\)
Th2:
\(x+\frac{3}{4}=-\frac{1}{3}\)
\(x=-\frac{1}{3}-\frac{3}{4}\)
\(x=-\frac{13}{12}\)
\(\left[\left(\frac{33}{5}-\frac{45}{14}\right).\frac{35}{6}\right]:\left[\left(21-1,25\right):2,5\right]\)
\(=\left[\left(\frac{462}{70}-\frac{225}{70}\right).\frac{35}{6}\right]:\left[19,75:2,5\right]\)
\(=\left[\frac{237}{70}.\frac{35}{6}\right]:7,9\)
\(=\frac{79}{4}:\frac{79}{10}\)
\(=\frac{79}{4}.\frac{10}{79}\)
\(=\frac{5}{2}\)
\(x\) \(\times\) \(\dfrac{14}{3}\) = 2,5
\(x\) = 2,5 : \(\dfrac{14}{3}\)
\(x\) = \(\dfrac{15}{28}\)
x.14/3=2,5
x =2,5:14/3
x =15/28
Chúc bn hok tốt!!!