Question

Answer 1

a) Ta có: \(20\%x-x+\dfrac{1}{5}=\dfrac{3}{4}\)

\(\Leftrightarrow\dfrac{-4}{5}x=\dfrac{3}{4}-\dfrac{1}{5}=\dfrac{11}{20}\)

hay \(x=-\dfrac{11}{16}\)

Vậy: \(x=-\dfrac{11}{16}\)

Answer 2

b) Ta có: \(\dfrac{2x+1}{3}=\dfrac{x-5}{2}\)

\(\Leftrightarrow2\left(2x+1\right)=3\left(x-5\right)\)

\(\Leftrightarrow4x+2=3x-15\)

\(\Leftrightarrow4x-3x=-15-2\)

hay x=-17

Vậy: x=-17

Answer 3

c) Ta có: \(\left(x-\dfrac{3}{4}\right)\left(4+3x\right)=0\)

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

Vậy: \(x\in\left\{\dfrac{3}{4};-\dfrac{4}{3}\right\}\)

Answer 4

d) Ta có: \(x-\dfrac{1}{3}x+\dfrac{1}{5}x=\dfrac{-26}{5}\)

\(\Leftrightarrow x\left(1-\dfrac{1}{3}+\dfrac{1}{5}\right)=-\dfrac{26}{5}\)

\(\Leftrightarrow x\cdot\dfrac{13}{15}=\dfrac{-26}{5}\)

hay \(x=-6\)

Vậy: x=-6

Answer 5

e) Ta có: \(50\%\cdot x+\dfrac{2}{3}x=x-5\)

\(\Leftrightarrow\dfrac{7}{6}x-x=-5\)

\(\Leftrightarrow\dfrac{1}{6}x=-5\)

hay x=-30

Vậy: x=-30

Answer 6

g) Ta có: \(\dfrac{2}{3}\left(x+\dfrac{9}{5}\right)-\dfrac{3}{10}\left(5x-\dfrac{1}{3}\right)=\dfrac{7}{15}\)

\(\Leftrightarrow\dfrac{2}{3}x+\dfrac{6}{5}-\dfrac{3}{2}x+\dfrac{1}{10}=\dfrac{7}{15}\)

\(\Leftrightarrow\dfrac{-5}{6}x=-\dfrac{5}{6}\)

hay x=1

Vậy: x=1

Answer 7

Giải:

a) \(20\%x-x+\dfrac{1}{5}=\dfrac{3}{4}\) 

        \(x.\left(20\%-1\right)=\dfrac{3}{4}-\dfrac{1}{5}\) 

                  \(x.\dfrac{-4}{5}=\dfrac{11}{20}\)  

                         \(x=\dfrac{11}{20}:\dfrac{-4}{5}\) 

                         \(x=\dfrac{-11}{16}\) 

b) \(\dfrac{2x+1}{3}=\dfrac{x-5}{2}\)

\(\Rightarrow2.\left(2x+1\right)=3.\left(x-5\right)\) 

          \(4x+2=3x-15\) 

        \(4x-3x=-15-2\) 

                 \(1x=-17\) 

                   \(x=-17:1\) 

                   \(x=-17\) 

c) \(\left(x-\dfrac{3}{4}\right).\left(4+3x\right)=0\) 

\(\Rightarrow x-\dfrac{3}{4}=0\) hoặc \(4+3x=0\) 

            \(x=\dfrac{3}{4}\) hoặc \(x=\dfrac{-4}{3}\) 

d) \(x-\dfrac{1}{3}x+\dfrac{1}{5}x=\dfrac{-26}{5}\) 

\(x.\left(1-\dfrac{1}{3}+\dfrac{1}{5}\right)=\dfrac{-26}{5}\) 

                  \(x.\dfrac{13}{15}=\dfrac{-26}{5}\) 

                        \(x=\dfrac{-26}{5}:\dfrac{13}{15}\) 

                        \(x=-6\) 

e) \(50\%x+\dfrac{2}{3}x=x-5\) 

\(50\%x+\dfrac{2}{3}x-x=-5\) 

\(x.\left(50\%+\dfrac{2}{3}-1\right)=-5\) 

                       \(x.\dfrac{1}{6}=-5\) 

                           \(x=-5:\dfrac{1}{6}\) 

                           \(x=-30\) 

g) \(\dfrac{2}{3}.\left(x+\dfrac{9}{5}\right)-\dfrac{3}{10}.\left(5x-\dfrac{1}{3}\right)=\dfrac{7}{15}\) 

                    \(\dfrac{2}{3}x+\dfrac{6}{5}-\dfrac{3}{2}x+\dfrac{1}{10}=\dfrac{7}{15}\) 

                                \(x.\left(\dfrac{2}{3}-\dfrac{3}{2}\right)=\dfrac{7}{15}-\dfrac{1}{10}-\dfrac{6}{5}\) 

                                          \(x.\dfrac{-5}{6}=\dfrac{-5}{6}\) 

                                                  \(x=\dfrac{-5}{6}:\dfrac{-5}{6}\) 

                                                 \(x=1\)