อนุพันธ์

$ y=\frac{7x+8}{9x^2+1} $

วิธีทำ

\begin{align} & \cssId{Step1}{ \frac{dy}{dx} = \frac{d}{dx} \frac{7x+8}{9x^2+1} } \\ &\cssId{Step2}{ =\frac{ (9x^2+1) \frac{d}{dx} (7x+8) - (7x+8) \frac{d}{dx} (9x^2+1) }{(9x^2+1)^2} } \\ &\cssId{Step3}{ = \frac{ (9x^2+1) 7 - (7x+8)(18x) }{(9x^2+1)^2} } \\ \end{align}