Câu 1.
`a)` `|5x-3|\ge 7`
$⇔\left[\begin{array}{l}5x-3\ge 7\\5x-3\le -7\end{array}\right.$
$⇔\left[\begin{array}{l}5x\ge 7+3\\5x\le -7+3\end{array}\right.$
$⇔\left[\begin{array}{l}5x\ge 10\\5x\le -4\end{array}\right.$
$⇔\left[\begin{array}{l}x\ge 2\\x\le \dfrac{-4}{5}\end{array}\right.$
Vậy `x\ge 2` hoặc `x\le {-4}/5`
$\\$
`b)` `x-2\sqrt{x}=0` ($ĐK: x\ge 0$)
`<=>\sqrt{x}(\sqrt{x}-2)=0`
$⇔\left[\begin{array}{l}\sqrt{x}=0\\\sqrt{x}-2=0\end{array}\right.$
$⇔\left[\begin{array}{l}x=0\\\sqrt{x}=2\end{array}\right.$
$⇔\left[\begin{array}{l}x=0(T M)\\x=4(T M)\end{array}\right.$
Vậy `x=0;x=4`
$\\$
Câu 2.
Ta có:
`\qquad {2012}/{4025}<{2012}/{4024}=1/ 2`
`\qquad {1999}/{3997}>{1999}/{3998}=1/ 2`
`=>{2012}/{4025}<{1999}/{3997}`
`=>{-2012}/{4025}>{-1999}/{3997}`
