Question

3) tìm x, biết

a) |x| = 1/2 ; b) |x| = 3,12 ; c) |x| = 0 ; d) |x| = 2 và 1/7

Answer 1

3) a) \(\left|x\right|=\dfrac{1}{2}\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=\dfrac{-1}{2}\end{matrix}\right.\) vậy \(x=\dfrac{1}{2};x=\dfrac{-1}{2}\)

b) \(\left|x\right|=3,12\Leftrightarrow\left[{}\begin{matrix}x=3,12\\x=-3,12\end{matrix}\right.\) vậy \(x=3,12;x=-3,12\)

c) \(\left|x\right|=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-0\end{matrix}\right.\) \(\Rightarrow x=0\) vậy \(x=0\)

d) th1: \(\left|x\right|=2\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)

th2: \(\left|x\right|=\dfrac{1}{7}\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{7}\\x=\dfrac{-1}{7}\end{matrix}\right.\)

vậy \(x=2;x=-2;x=\dfrac{1}{7};x=\dfrac{-1}{7}\)