Question

Tìm x biết

|5x-3|\(\ge\)7

Answer 1

|5x-3|$\ge$7

TH1: 5x-3\(\ge7\)

<->x \(\ge2\)

TH2:5x-3\(\ge-7\)

<-> x\(\ge\frac{-4}{5}\)

Answer 2

Ta có: \(\left|5x-3\right|\ge7\)

\(\Rightarrow\left[{}\begin{matrix}5x-3\ge7\\5x-3\le-7\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}5x\ge10\\5x\le-4\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x\ge2\\x\le-0,8\end{matrix}\right.\)

Vì x∈Z nên \(x\ge2\)

Vậy: \(x\ge2\)

Answer 3

\(\left|5x-3\right|\ge7\)

\(\Rightarrow\left[{}\begin{matrix}5x-3\ge7\\5x-3\le-7\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}5x\ge10\\5x\le-4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x\ge10:5\\x\le\left(-4\right):5\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x\ge2\\x\le-\frac{4}{5}\end{matrix}\right.\)

Vậy \(x\ge2\) hoặc \(x\le-\frac{4}{5}\) thì \(\left|5x-3\right|\ge7.\)

Chúc bạn học tốt!