Question

Tìm x

|x+1|+|x+4|=3x
|3x-5|-1/7=1/3

Answer 1

a, \(\left\{{}\begin{matrix}\left|x+1\right|\ge0\\\left|x+4\right|\ge0\end{matrix}\right.\Rightarrow\left|x+1\right|+\left|x+4\right|\ge0\)

\(\Rightarrow3x\ge0\Rightarrow x\ge0\)

\(\Rightarrow x+1+x+4=3x\Rightarrow x=5\)

Vậy x = 5

b, \(\left|3x-5\right|-\dfrac{1}{7}=\dfrac{1}{3}\)

\(\Rightarrow\left|3x-5\right|=\dfrac{10}{21}\)

+) Xét \(x\ge\dfrac{5}{3}\) có:
\(3x-5=\dfrac{10}{21}\Rightarrow x=\dfrac{115}{63}\) ( t/m )
+) Xét \(x< \dfrac{5}{3}\) có:

\(5-3x=\dfrac{10}{21}\Rightarrow x=\dfrac{95}{63}\) ( t/m )

Vậy...