Question 12 Marks
If $y =\frac{ e ^x}{\sqrt{x}}$, find $\frac{d y}{d x}$ when $x =1$
Answer
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y=\frac{ e ^x}{\sqrt{x}}
$
Differentiating w.r.t. $x$, we get
$
\begin{aligned}
\frac{ d y}{ d x} & =\frac{ d }{ d x}\left(\frac{ e ^x}{\sqrt{x}}\right) \\
& =\frac{\sqrt{x} \frac{ d }{ d x} e ^x- e ^x \frac{ d }{ d x} \sqrt{x}}{(\sqrt{x})^2} \\
& =\frac{\sqrt{x} e ^x- e ^x \frac{1}{2 \sqrt{x}}}{x} \\
\frac{ d y}{ d x} & =\frac{2 x \cdot e ^x- e ^x}{2 \sqrt{x} x}
\end{aligned}
$
When $x=1$,
$
\frac{ d y}{ d x}=\frac{2(1) e ^1- e ^{ l }}{2 \sqrt{1} .1}=\frac{2 e - e }{2}=\frac{ e }{2}
$
y=\frac{ e ^x}{\sqrt{x}}
$
Differentiating w.r.t. $x$, we get
$
\begin{aligned}
\frac{ d y}{ d x} & =\frac{ d }{ d x}\left(\frac{ e ^x}{\sqrt{x}}\right) \\
& =\frac{\sqrt{x} \frac{ d }{ d x} e ^x- e ^x \frac{ d }{ d x} \sqrt{x}}{(\sqrt{x})^2} \\
& =\frac{\sqrt{x} e ^x- e ^x \frac{1}{2 \sqrt{x}}}{x} \\
\frac{ d y}{ d x} & =\frac{2 x \cdot e ^x- e ^x}{2 \sqrt{x} x}
\end{aligned}
$
When $x=1$,
$
\frac{ d y}{ d x}=\frac{2(1) e ^1- e ^{ l }}{2 \sqrt{1} .1}=\frac{2 e - e }{2}=\frac{ e }{2}
$