21/5 + 3:|x/4-2/3|=6
=>3:|x/4-2/3|=6-21/5
=>|x/4-2/3|=3:9/5=5/3
ta có 2 th
TH1 x/4-2/3=5/3
=>x/4=2 =>x=8
TH2 x/4-2/3=-5/3
=>x/4=-1 =>x=-4
vậy x thuộc {-4;8}
nhớ cho mik
Bạn ơi, cho mk hỏi:
Tại sao lại từ x/4 - 2/3 = 5/3 lại suy ra x/4 = 2.
\(\frac{21}{5}+3\div\left|\frac{x}{4}-\frac{2}{3}\right|=6\)
\(\Rightarrow3\div\left|\frac{x}{4}-\frac{2}{3}\right|=6-\frac{21}{5}\)
\(\Rightarrow3\div\left|\frac{x}{4}-\frac{2}{3}\right|=\frac{9}{5}\)
\(\Rightarrow\left|\frac{x}{4}-\frac{2}{3}\right|=3\div\frac{9}{5}\)
\(\Rightarrow\left|\frac{x}{4}-\frac{2}{3}\right|=\frac{5}{3}\)
\(\Rightarrow\orbr{\begin{cases}\frac{x}{4}-\frac{2}{3}=\frac{5}{3}\\\frac{x}{4}-\frac{2}{3}=\frac{-5}{3}\end{cases}\Rightarrow\orbr{\begin{cases}\frac{x}{4}=\frac{5}{3}+\frac{2}{3}\\\frac{x}{4}=\frac{-5}{3}+\frac{2}{3}\end{cases}}}\)
\(\Rightarrow\orbr{\begin{cases}\frac{x}{4}=\frac{7}{3}\\\frac{x}{4}=-1\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{7}{3}.4\\x=-1.4\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{28}{3}\\x=-4\end{cases}}}\)
Vậy \(x=\frac{28}{3}\) hoặc \(x=-4\)
