第110回薬剤師国家試験

$\begin{tikzpicture}[declare function = {kel=0.5;f(\x)=(ln(\x)-ln(kel))/(\x-kel);}]\draw[thick, < - >, >=stealth] (0,3) node[below left]{$t_{\rm max}$} -- (0,0) node[below left=-1mm]{$0$} -- (6,0)node[below left]{$k_{\rm a}$};\draw[very thick, domain=0.22:6,samples=200, blue] plot(\x,{f(\x)});\end{tikzpicture}$

$t_{\rm max}=-\dfrac{\ \ln \dfrac{\ k_{\rm el}\ }{k_{\rm a}}\ }{\ k_{\rm a}-k_{\rm el}\ }=\dfrac{\ \ln \dfrac{k_{\rm a}}{\ k_{\rm el}\ }\ }{\ k_{\rm a}-k_{\rm el}\ }=\dfrac{\ \ln k_{\rm a}-\ln k_{\rm el}\ }{k_{\rm a}-k_{\rm el}}=\dfrac{\ \ln k_{\rm el}-\ln k_{\rm a}\ }{k_{\rm el}-k_{\rm a}}$

\begin{tikzpicture}[
declare function = {
kel=0.5;
f(\x)=(ln(\x)-ln(kel))/(\x-kel);
}]
\draw[thick, < - >, >=stealth] (0,3) node[below left]{$t_{\rm max}$} -- (0,0) node[below left=-1mm]{$0$} -- (6,0)node[below left]{$k_{\rm a}$};
\draw[very thick, domain=0.22:6,samples=200, blue] plot(\x,{f(\x)});
\end{tikzpicture}