Bài 1:
a) \(\left|3x+1\right|>4\)
\(\Rightarrow\left[{}\begin{matrix}3x+1>4\\3x+1< -4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}3x>3\\3x< -5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x>3:3\\x< \left(-5\right):3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x>1\\x< -\frac{5}{3}\end{matrix}\right.\)
Vậy \(x>1\) hoặc \(x< -\frac{5}{3}\) thì \(\left|3x+1\right|>4.\)
b) \(\left|4-x\right|+2x=3\)
\(\Rightarrow\left|4-x\right|=3-2x\)
\(\Rightarrow\left[{}\begin{matrix}4-x=3-2x\\4-x=2x-3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}4-3=-2x+x\\4+3=2x+x\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}1=-1x\\7=3x\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=1:\left(-1\right)\\x=7:3\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=\frac{7}{3}\end{matrix}\right.\)
Vì \(x\in Z.\)
\(\Rightarrow x=-1.\)
Vậy \(x=-1.\)
Chúc bạn học tót!
bài 2:
a=3
b=2
c=6
