Question

Answer 1

20/ \(y'=-2x+4>0\Leftrightarrow x< 2\Rightarrow x\in\left(-\infty;2\right)\)

21/\(\left\{{}\begin{matrix}AB=CD\\\overrightarrow{AB}\uparrow\downarrow\overrightarrow{CD}\end{matrix}\right.\Rightarrow\overrightarrow{AB}+\overrightarrow{CD}=\overrightarrow{0}\)

23/\(y'=m+5;\left\{{}\begin{matrix}y'>0\Leftrightarrow m>-5\\y'< 0\Leftrightarrow m< -5\end{matrix}\right.\Rightarrow A\)