Question

3. tìm x

a. \(\dfrac{1}{5}+x=\dfrac{-1}{2}\)

b. \(1\dfrac{3}{4}.x+1\dfrac{1}{2}=\dfrac{-4}{5}\)

c.\(\left|x+\dfrac{3}{4}\right|-5=-2\)

d.\(\dfrac{-5}{8}+x=\dfrac{4}{9}\)

Answer 1

a) \(\dfrac{1}{5}+x=-\dfrac{1}{2}\)

\(x=-\dfrac{1}{2}-\dfrac{1}{5}=-\dfrac{7}{10}\)

b) \(1\dfrac{3}{4}x+1\dfrac{1}{2}=-\dfrac{4}{5}\)

\(\dfrac{7}{4}x+\dfrac{3}{2}=-\dfrac{4}{5}\)

\(\dfrac{7}{4}x=-\dfrac{4}{5}-\dfrac{3}{2}=-\dfrac{23}{10}\)

\(x=\dfrac{-47}{35}\)

c) \(\left|x+\dfrac{3}{4}\right|-5=-2\)

\(\left|x+\dfrac{3}{4}\right|=-2+5=3\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{3}{4}=3\\x+\dfrac{3}{4}=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{9}{4}\\x=-\dfrac{15}{4}\end{matrix}\right.\)

d) \(-\dfrac{5}{8}+x=\dfrac{4}{9}\)

\(x=\dfrac{4}{9}+\dfrac{5}{8}\)

\(x=\dfrac{77}{72}\)