Question Number 220224 by Mamadi last updated on 09/May/25

$${calcul}\:{together}\:{of}\:{definition}\:{of}\:{and} \\ $$$${calcul}\:{the}\:{derive}\:{f}^{\:} \:^{'} \\ $$$${f}\left({x}\right)=\:\:{x}\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}} \\ $$
Answered by hlwrc last updated on 09/May/25

$$\frac{{df}\left({x}\right)}{{dx}}=\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}}+\frac{{x}}{\mathrm{2}}\sqrt{\frac{{x}+\mathrm{1}}{{x}−\mathrm{1}}}×\frac{\left({x}−\mathrm{1}\right)−\left({x}+\mathrm{1}\right)}{\left({x}+\mathrm{1}\right)^{\mathrm{2}} } \\ $$$$==\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}}−\frac{\mathrm{2}{x}}{\mathrm{2}\left({x}+\mathrm{1}\right)\sqrt{\left({x}+\mathrm{1}\right)\left({x}−\mathrm{1}\right)}} \\ $$$$ \\ $$$$ \\ $$$$ \\ $$$$ \\ $$
Answered by efronzo1 last updated on 09/May/25

$$\:\mathrm{f}\left(\mathrm{x}\right)\:=\sqrt{\frac{\mathrm{x}^{\mathrm{3}} −\mathrm{x}^{\mathrm{2}} }{\mathrm{x}+\mathrm{1}}}\: \\ $$$$\:\mathrm{f}\:'\left(\mathrm{x}\right)\:=\:\frac{\frac{\left(\mathrm{3x}^{\mathrm{2}} −\mathrm{2x}\right)\left(\mathrm{x}+\mathrm{1}\right)−\left(\mathrm{x}^{\mathrm{3}} −\mathrm{x}^{\mathrm{2}} \right)}{\left(\mathrm{x}+\mathrm{1}\right)^{\mathrm{2}} }}{\mathrm{2}\sqrt{\frac{\mathrm{x}^{\mathrm{3}} −\mathrm{x}^{\mathrm{2}} }{\mathrm{x}+\mathrm{1}}}} \\ $$
Answered by Frix last updated on 10/May/25

$${f}\left({x}\right)=\frac{{x}\sqrt{{x}−\mathrm{1}}}{\:\sqrt{{x}+\mathrm{1}}}=\frac{{u}}{{v}}\:\Rightarrow\:{f}'\left({x}\right)=\frac{{u}'{v}−{v}'{u}}{{v}^{\mathrm{2}} } \\ $$$${u}={gh}\:\Rightarrow\:{u}'={g}'{h}+{h}'{g} \\ $$$${g}={x}\:\Rightarrow\:{g}'=\mathrm{1} \\ $$$${h}=\sqrt{{x}−\mathrm{1}}\:\Rightarrow\:{h}'=\frac{\mathrm{1}}{\mathrm{2}\sqrt{{x}−\mathrm{1}}} \\ $$$${v}=\sqrt{{x}+\mathrm{1}}\:\Rightarrow\:{v}'=\frac{\mathrm{1}}{\mathrm{2}\sqrt{{x}+\mathrm{1}}} \\ $$$${f}'\left({x}\right)=\frac{\left({g}'{h}+{h}'{g}\right){v}−{v}'{gh}}{{v}^{\mathrm{2}} }= \\ $$$$=\frac{\left(\sqrt{{x}−\mathrm{1}}+\frac{{x}}{\mathrm{2}\sqrt{{x}−\mathrm{1}}}\right)\sqrt{{x}+\mathrm{1}}−\frac{{x}\sqrt{{x}−\mathrm{1}}}{\mathrm{2}\sqrt{{x}+\mathrm{1}}}}{{x}+\mathrm{1}}= \\ $$$$… \\ $$$$=\frac{{x}^{\mathrm{2}} +{x}−\mathrm{1}}{\:\sqrt{\left({x}+\mathrm{1}\right)^{\mathrm{3}} \left({x}−\mathrm{1}\right)}} \\ $$
Answered by Ghisom last updated on 10/May/25

$${t}=\frac{\sqrt{{x}−\mathrm{1}}}{\:\sqrt{{x}+\mathrm{1}}}\:\Leftrightarrow\:{x}=−\frac{{t}^{\mathrm{2}} +\mathrm{1}}{{t}^{\mathrm{2}} −\mathrm{1}} \\ $$$${f}\left({t}\right)=−\frac{\left({t}^{\mathrm{2}} +\mathrm{1}\right){t}}{{t}^{\mathrm{2}} −\mathrm{1}}=\frac{{u}}{{v}} \\ $$$${f}\:'\left({t}\right)=\frac{{u}'{v}−{v}'{u}}{{v}^{\mathrm{2}} }{dt}=−\frac{{t}^{\mathrm{4}} −\mathrm{4}{t}^{\mathrm{2}} −\mathrm{1}}{\left({t}^{\mathrm{2}} −\mathrm{1}\right)^{\mathrm{2}} }{dt} \\ $$$${t}=\frac{\sqrt{{x}−\mathrm{1}}}{\:\sqrt{{x}+\mathrm{1}}}\:\rightarrow\:{dt}={t}'=\frac{\mathrm{1}}{\:\sqrt{\left({x}+\mathrm{1}\right)^{\mathrm{3}} \left({x}−\mathrm{1}\right)}} \\ $$$${f}\:'\left({x}\right)=\frac{{x}^{\mathrm{2}} +{x}−\mathrm{1}}{\:\sqrt{\left({x}+\mathrm{1}\right)^{\mathrm{3}} \left({x}−\mathrm{1}\right)}} \\ $$
Answered by Marzuk last updated on 10/May/25
![1.(d/dx)[f(x).g(x)]=f ′(x)g(x)+f(x)g′(x) 2.(d/dx) [((f(x))/(g(x)))] = ((f ′(x)g(x)−f(x)g′(x))/([g(x)]^2 )) 3.(d/dx)[f(x)^n ] = nf(x)^(n−1) . f ′(x) ∴ (df/dx) = (√((x−1)/(x+1))) + x (d/dx)[(√((x−1)/(x+1)))] [app. 1.] =(√(((x−1)/(x+1)) )) + x[(1/2)((√((x−1)/(x+1))))^(−(1/2)) . (((x+1)−(x−1))/((x+1)^2 ))] [app. 2. 3.] ∴](https://www.tinkutara.com/question/Q220240.png)
$$\mathrm{1}.\frac{{d}}{{dx}}\left[{f}\left({x}\right).{g}\left({x}\right)\right]={f}\:'\left({x}\right){g}\left({x}\right)+{f}\left({x}\right){g}'\left({x}\right) \\ $$$$\mathrm{2}.\frac{{d}}{{dx}}\:\left[\frac{{f}\left({x}\right)}{{g}\left({x}\right)}\right]\:=\:\frac{{f}\:'\left({x}\right){g}\left({x}\right)−{f}\left({x}\right){g}'\left({x}\right)}{\left[{g}\left({x}\right)\right]^{\mathrm{2}} } \\ $$$$\mathrm{3}.\frac{{d}}{{dx}}\left[{f}\left({x}\right)^{{n}} \right]\:=\:{nf}\left({x}\right)^{{n}−\mathrm{1}} \:.\:{f}\:'\left({x}\right) \\ $$$$\therefore\:\frac{{df}}{{dx}}\:=\:\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}}\:+\:{x}\:\frac{{d}}{{dx}}\left[\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}}\right]\:\left[{app}.\:\mathrm{1}.\right] \\ $$$$\:\:\:\:\:\:\:\:\:\:\:=\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}\:}\:+\:{x}\left[\frac{\mathrm{1}}{\mathrm{2}}\left(\sqrt{\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}}\right)^{−\frac{\mathrm{1}}{\mathrm{2}}} .\:\frac{\left({x}+\mathrm{1}\right)−\left({x}−\mathrm{1}\right)}{\left({x}+\mathrm{1}\right)^{\mathrm{2}} }\right]\:\left[{app}.\:\mathrm{2}.\:\mathrm{3}.\right] \\ $$$$\therefore\: \\ $$