Câu hỏi của RF huy

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tìm x biết a,$\left|2x+\frac{3}{4}\right|=\frac{1}{2}$b,$\frac{3x}{2,7}=\frac{\frac{1}{4}}{2\frac{1}{4}}$c,$\left|x-1\right|+4=6$d, $\frac{x}{3}=\frac{y}{5}$ và y-x=24e, \(\left(x^2-3\right)^2...

Nguyễn Thị Yến Nhi · Accepted Answer

a) $\left|2x+\frac{3}{4}\right|=\frac{1}{2}$     $\orbr{\begin{cases}2x+\frac{3}{4}=\frac{1}{2}\2x+\frac{3}{4}=\frac{-1}{2}\end{cases}}$ =>   $\orbr{\begin{cases}2x=\frac{1}{2}-\frac{3}{4}\2x=\frac{-1}{2}-\frac{3}{4}\end{cases}}$  =>   $\orbr{\begin{cases}2x=\frac{-1}{4}\2x=\frac{-5}{4}\end{cases}}$ =>   $\orbr{\begin{cases}x=\frac{-1}{8}\x=\frac{-5}{8}\end{cases}}$Vậy $x=\left\{\frac{-1}{8},\frac{-5}{8}\right\}$b) $\frac{3x}{2,7}=\frac{\frac{1}{4}}{2\frac{1}{4}}$= $\frac{3x}{2,7}=\frac{\frac{1}{4}}{\frac{9}{4}}$=> $3x.\frac{9}{4}=2,7.\frac{1}{4}$=>  $\frac{27x}{4}=\frac{27}{40}$$27x.40=27.4$$1080.x=108$             $x=\frac{1}{10}$Vậy $x=\frac{1}{10}$c) $\left|x-1\right|+4=6$$\left|x-1\right|=6-4$$\left|x-1\right|=2$$\orbr{\begin{cases}x-1=2\x-1=-2\end{cases}}$=>  $\orbr{\begin{cases}x=3\x=-1\end{cases}}$Vậy $x=\left[3,-1\right]$d) $\frac{x}{3}=\frac{y}{5}=>\frac{y}{5}=\frac{x}{3}=>\frac{y-x}{5-3}=\frac{24}{2}=12$e) $\left(x^2-3\right)^2=16$$\left(x^2-3\right)^2=4^2$$=>x^2-3=4$$x^2=7=>x=\sqrt{7}$Vậy $x=\sqrt{7}$f) $\frac{3}{4}+\frac{2}{5}x=\frac{29}{60}$               $\frac{2}{5}x=\frac{29}{60}-\frac{3}{4}$                $\frac{2}{5}x=-\frac{4}{15}$          $x=-\frac{4}{15}:\frac{2}{5}=-\frac{4}{15}.\frac{5}{2}=-\frac{2}{3}$Vậy $x=-\frac{2}{3}$g) $\left(-\frac{1}{3}\right)^3.x=\frac{1}{81}$$\left(-\frac{1}{27}\right).x=\frac{1}{81}$$x=\left(-\frac{1}{27}\right):\frac{1}{81}=\left(-\frac{1}{27}\right).81=-3$Vậy $x=-3$k)$\frac{3}{4}-\frac{2}{5}x=\frac{29}{60}$$\frac{2}{5}x=\frac{3}{4}-\frac{29}{60}$$\frac{2}{5}x=\frac{4}{15}$      $x=\frac{2}{5}-\frac{4}{15}=>x=\frac{2}{15}$Vậy $x=\frac{2}{15}$I) $\frac{3}{5}x-\frac{1}{2}=-\frac{1}{7}$$\frac{3}{5}x=-\frac{1}{7}+\frac{1}{2}$$\frac{3}{5}x=\frac{5}{14}$$x=\frac{5}{14}:\frac{3}{5}=\frac{5}{14}.\frac{5}{3}=\frac{25}{42}$Vậy $x=\frac{25}{42}$Câu trả lời: a) $\left|2x+\frac{3}{4}\right|=\frac{1}{2}$     $\orbr{\begin{cases}2x+\frac{3}{4}=\frac{1}{2}\2x+\frac{3}{4}=\frac{-1}{2}\end{cases}}$ =>   $\orbr{\begin{cases}2x=\frac{1}{2}-\frac{3}{4}\2x=\frac{-1}{2}-\frac{3}{4}\end{cases}}$  =>   $\orbr{\begin{cases}2x=\frac{-1}{4}\2x=\frac{-5}{4}\end{cases}}$ =>   $\orbr{\begin{cases}x=\frac{-1}{8}\x=\frac{-5}{8}\end{cases}}$Vậy $x=\left\{\frac{-1}{8},\frac{-5}{8}\right\}$b) $\frac{3x}{2,7}=\frac{\frac{1}{4}}{2\frac{1}{4}}$= $\frac{3x}{2,7}=\frac{\frac{1}{4}}{\frac{9}{4}}$=> $3x.\frac{9}{4}=2,7.\frac{1}{4}$=>  $\frac{27x}{4}=\frac{27}{40}$$27x.40=27.4$$1080.x=108$             $x=\frac{1}{10}$Vậy $x=\frac{1}{10}$c) $\left|x-1\right|+4=6$$\left|x-1\right|=6-4$$\left|x-1\right|=2$$\orbr{\begin{cases}x-1=2\x-1=-2\end{cases}}$=>  $\orbr{\begin{cases}x=3\x=-1\end{cases}}$Vậy $x=\left[3,-1\right]$d) $\frac{x}{3}=\frac{y}{5}=>\frac{y}{5}=\frac{x}{3}=>\frac{y-x}{5-3}=\frac{24}{2}=12$e) $\left(x^2-3\right)^2=16$$\left(x^2-3\right)^2=4^2$$=>x^2-3=4$$x^2=7=>x=\sqrt{7}$Vậy $x=\sqrt{7}$f) $\frac{3}{4}+\frac{2}{5}x=\frac{29}{60}$               $\frac{2}{5}x=\frac{29}{60}-\frac{3}{4}$                $\frac{2}{5}x=-\frac{4}{15}$          $x=-\frac{4}{15}:\frac{2}{5}=-\frac{4}{15}.\frac{5}{2}=-\frac{2}{3}$Vậy $x=-\frac{2}{3}$g) $\left(-\frac{1}{3}\right)^3.x=\frac{1}{81}$$\left(-\frac{1}{27}\right).x=\frac{1}{81}$$x=\left(-\frac{1}{27}\right):\frac{1}{81}=\left(-\frac{1}{27}\right).81=-3$Vậy $x=-3$k)$\frac{3}{4}-\frac{2}{5}x=\frac{29}{60}$$\frac{2}{5}x=\frac{3}{4}-\frac{29}{60}$$\frac{2}{5}x=\frac{4}{15}$      $x=\frac{2}{5}-\frac{4}{15}=>x=\frac{2}{15}$Vậy $x=\frac{2}{15}$I) $\frac{3}{5}x-\frac{1}{2}=-\frac{1}{7}$$\frac{3}{5}x=-\frac{1}{7}+\frac{1}{2}$$\frac{3}{5}x=\frac{5}{14}$$x=\frac{5}{14}:\frac{3}{5}=\frac{5}{14}.\frac{5}{3}=\frac{25}{42}$Vậy $x=\frac{25}{42}$

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