Đạo ham Giúp mk 3 câu này nha Question Đạo ham Giúp mk 3 câu này nha in progress 0 Môn Toán Thu Cúc 5 years 2021-05-16T02:50:28+00:00 2021-05-16T02:50:28+00:00 2 Answers 27 views 0
Answers ( )
Đáp án:
\(\begin{array}{l}
4)\quad y’ = \dfrac{2x+1}{2(x+1)\sqrt{x+1}}\\
5)\quad y’ = – \dfrac{1}{(\sin x – \cos x)^2}\\
6)\quad y’ = \dfrac{-2}{\cos^2(-2x+3)}
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
4)\quad y = \dfrac{2x+3}{\sqrt{x+1}}\\
\to y’ = \dfrac{(2x+3)’\sqrt{x+1} – (2x+3).\left(\sqrt{x+1}\right)’}{x+1}\\
\to y’ = \dfrac{2\sqrt{x+1} – (2x+3)\cdot\dfrac{(x+1)’}{2\sqrt{x+1}}}{x+1}\\
\to y’ = \dfrac{2\sqrt{x+1} – (2x+3)\cdot\dfrac{1}{2\sqrt{x+1}}}{x+1}\\
\to y’ = \dfrac{\dfrac{4(x+1) – (2x+3)}{2\sqrt{x+1}}}{x+1}\\
\to y’ = \dfrac{2x+1}{2(x+1)\sqrt{x+1}}\\
5)\quad y = \dfrac{\sin x}{\sin x – \cos x}\\
\to y’ = \dfrac{(\sin x)'(\sin x – \cos x) – \sin x(\sin x – \cos x)’}{(\sin x – \cos x)^2}\\
\to y’ = \dfrac{\cos x(\sin x – \cos x) – \sin x(\cos x + \sin x)}{(\sin x – \cos x)^2}\\
\to y’ = \dfrac{-\sin^2x – \cos^2x}{(\sin x – \cos x)^2}\\
\to y’ = – \dfrac{1}{(\sin x – \cos x)^2}\\
6)\quad y = \tan(-2x+3)\\
\to y’ = \dfrac{(-2x+3)’}{\cos^2(-2x+3)}\\
\to y’ = \dfrac{-2}{\cos^2(-2x+3)}
\end{array}\)
4.
$y’=\dfrac{2\sqrt{x+1}-(2x+3).(\sqrt{x+1})’ }{\sqrt{x+1}^2}$
$=\dfrac{2\sqrt{x+1}-(2x+3).\dfrac{1}{2\sqrt{x+1}} }{x+1}$
$=\dfrac{4(x+1)-(2x+3)}{(x+1).2\sqrt{x+1}}$
$=\dfrac{2x+1}{2\sqrt{x+1}(x+1)}$
5.
$y’=1:\dfrac{\sin x-\cos x}{\sin x}$
$=1:\Big(1-\cot x\Big)$
$=\dfrac{1}{1-\cot x}$
$y’=-\dfrac{(1-\cot x)’}{(1-\cot x)^2}$
$=-\dfrac{1+\sin^2x}{(1-\cot x)^2}$
6.
$y’=\dfrac{(-2x+3)’}{\cos^2(-2x+3)}$
$=\dfrac{-2}{2\cos^2(-2x+3)}$