[tex]\dfrac{d}{dx} \left(\dfrac{x+9}{x+1}\right)\\\\\\=\dfrac{(x+1)\dfrac{d}{dx}(x+9) - (x+9) \dfrac{d}{dx}(x+1)}{(x+1)^2}\\\\\\=\dfrac{(x+1) - (x+9)}{(x+1)^2}\\\\\\=\dfrac{x+1-x-9}{(x+1)^2}\\\\\\=-\dfrac{8}{(x+1)^2}[/tex]
