Tìm x, biết: a) 29:x+56=0,5 b) 34−x−23=113 c) 114:x−23=0,75 d) −56x+54:32=43

Câu hỏi:

Tìm x, biết:
a) $\frac{2}{9}:x+\frac{5}{6}=0,5$
b) $\frac{3}{4}-\left(x-\frac{2}{3}\right)=1\frac{1}{3}$
c) $1\frac{1}{4}:\left(x-\frac{2}{3}\right)=0,75$
d) $\left(-\frac{5}{6}x+\frac{5}{4}\right):\frac{3}{2}=\frac{4}{3}$

Trả lời:

a) $\frac{2}{9}:x+\frac{5}{6}=0,5$
$\frac{2}{9}:x=\frac{1}{2}-\frac{5}{6}$
$\frac{2}{9}:x=\frac{3}{6}-\frac{5}{6}$
$\frac{2}{9}:x=\frac{-2}{6}$
$x=\frac{2}{9}:\frac{-2}{6}$
$x=\frac{2}{9}.\frac{6}{-2}$
$x=\frac{-2}{3}$
Vậy $x=\frac{-2}{3}$
b) $\frac{3}{4}-\left(x-\frac{2}{3}\right)=1\frac{1}{3}$
$\frac{3}{4}-\left(x-\frac{2}{3}\right)=\frac{4}{3}$
$x-\frac{2}{3}=\frac{3}{4}-\frac{4}{3}$
$x-\frac{2}{3}=\frac{9}{12}-\frac{16}{12}$
$x-\frac{2}{3}=\frac{-7}{12}$
$x=\frac{-7}{12}+\frac{2}{3}$
$x=\frac{-7}{12}+\frac{8}{12}$
$x=\frac{1}{12}$
Vậy $x=\frac{1}{12}$
c) $1\frac{1}{4}:\left(x-\frac{2}{3}\right)=0,75$
$\frac{5}{4}:\left(x-\frac{2}{3}\right)=\frac{3}{4}$
$x-\frac{2}{3}=\frac{5}{4}:\frac{3}{4}$
$x-\frac{2}{3}=\frac{5}{4}.\frac{4}{3}$
$x-\frac{2}{3}=\frac{5}{3}$
$x=\frac{5}{3}+\frac{2}{3}$
$x=\frac{7}{3}$
d) $\left(-\frac{5}{6}x+\frac{5}{4}\right):\frac{3}{2}=\frac{4}{3}$
$-\frac{5}{6}x+\frac{5}{4}=\frac{4}{3}.\frac{3}{2}$
$-\frac{5}{6}x+\frac{5}{4}=2$
$-\frac{5}{6}x=2-\frac{5}{4}$
$-\frac{5}{6}x=\frac{8}{4}-\frac{5}{4}$
$-\frac{5}{6}x=\frac{3}{4}$
$x=\frac{3}{4}:\left(-\frac{5}{6}\right)$
$x=\frac{3}{4}.\frac{-6}{5}$
$x=\frac{-9}{10}$
Vậy $x=\frac{-9}{10}$
 

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1. Tính nhanh:
   a) 1323.711+1023.711
   b) 59.2311−111.59+59
   c) −49+35:1317+25−59:1317
   d) 316:322−311+316:110−25

   Câu hỏi:
   

   Tính nhanh:
   a) $\frac{13}{23}.\frac{7}{11}+\frac{10}{23}.\frac{7}{11}$
   b) $\frac{5}{9}.\frac{23}{11}-\frac{1}{11}.\frac{5}{9}+\frac{5}{9}$
   c) $\left[\left(-\frac{4}{9}\right)+\frac{3}{5}\right]:\frac{13}{17}+\left(\frac{2}{5}-\frac{5}{9}\right):\frac{13}{17}$
   d) $\frac{3}{16}:\left(\frac{3}{22}-\frac{3}{11}\right)+\frac{3}{16}:\left(\frac{1}{10}-\frac{2}{5}\right)$

   Trả lời:

   a) $\frac{13}{23}.\frac{7}{11}+\frac{10}{23}.\frac{7}{11}$
   $=\frac{7}{11}.\left(\frac{13}{23}+\frac{10}{23}\right)$
   $=\frac{7}{11}.\frac{23}{23}=\frac{7}{11}.1=\frac{7}{11}$
   b) $\frac{5}{9}.\frac{23}{11}-\frac{1}{11}.\frac{5}{9}+\frac{5}{9}$
   $=\frac{5}{9}.\left(\frac{23}{11}-\frac{1}{11}+1\right)$
   $=\frac{5}{9}.\left(\frac{22}{11}+1\right)$
   $=\frac{5}{9}.\left(2+1\right)$
   $=\frac{5}{9}.3=\frac{5}{3}$
   c) $\left[\left(-\frac{4}{9}\right)+\frac{3}{5}\right]:\frac{13}{17}+\left(\frac{2}{5}-\frac{5}{9}\right):\frac{13}{17}$
   $=\left[\left(-\frac{4}{9}\right)+\frac{3}{5}\right].\frac{17}{13}+\left(\frac{2}{5}-\frac{5}{9}\right).\frac{17}{13}$
   $=\left(-\frac{4}{9}+\frac{3}{5}+\frac{2}{5}-\frac{5}{9}\right).\frac{17}{13}$
   $=\left(\frac{-4-5}{9}+\frac{3+2}{5}\right).\frac{17}{13}$
   $=\left(\frac{-9}{9}+\frac{5}{5}\right).\frac{17}{13}$
   $=\left(-1+1\right).\frac{17}{13}$
   $=0.\frac{17}{13}=0$
   d) $\frac{3}{16}:\left(\frac{3}{22}-\frac{3}{11}\right)+\frac{3}{16}:\left(\frac{1}{10}-\frac{2}{5}\right)$
   $=\frac{3}{16}:\left(\frac{3}{22}-\frac{6}{22}\right)+\frac{3}{16}:\left(\frac{1}{10}-\frac{4}{10}\right)$
   $=\frac{3}{16}:\frac{-3}{22}+\frac{3}{16}:\frac{-3}{10}$
   $=\frac{3}{16}.\frac{22}{-3}+\frac{3}{16}.\frac{10}{-3}$
   $=\frac{3}{16}.\left(\frac{22}{-3}+\frac{10}{-3}\right)$
   $=\frac{3}{16}.\frac{32}{-3}$
   $=\frac{\mathrm{3.16.2}}{\mathrm{16.3.}(-1)}=-2$

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