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Calculus1 18 Online
OpenStudy (anonymous):

How do I simplify this?

OpenStudy (anonymous):

\[\frac{ 1+\sqrt{x}-\frac{ 1 }{ 2 }x (x) ^{-1/2} }{ (1+\sqrt{x})^2 }\]

OpenStudy (anonymous):

Those are square roots over those 'x's by the way. The answer is supposed to be \[\frac{ 2+ \sqrt{x} }{ 2 (1+\sqrt{x})^2 }\] but I don't understand how they got there.

OpenStudy (solomonzelman):

" Those are square roots over those 'x's " ? can you then please show what the problem really is like?

OpenStudy (anonymous):

It was to find the derivative of \[\frac{ x }{ 1+\sqrt{x} }\]

OpenStudy (solomonzelman):

oh

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle \frac{x}{1+\sqrt{x}} }\) the first option is to use the quotient rule

OpenStudy (solomonzelman):

well, or you can say, \(\large\color{black}{ \displaystyle x(1+\sqrt{x})^{-1} }\) and use the product rule

OpenStudy (anonymous):

Yeah I used the quotient rule to get that

OpenStudy (solomonzelman):

or you can do logarithmic differentiation \(\large\color{black}{ \displaystyle y=\frac{x}{1+\sqrt{x}} }\) \(\large\color{black}{ \displaystyle \ln (y)=\ln\left( \frac{x}{1+\sqrt{x}}\right) }\) \(\large\color{black}{ \displaystyle \ln y=\ln x -\ln(1+\sqrt{x}) }\) and on....

OpenStudy (anonymous):

But I was just wondering if you knew how I would simplify something like that?

OpenStudy (anonymous):

using the quotient rule

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle \frac{ (x)'(1+\sqrt{x})-(x)(1+\sqrt{x})' }{(1+\sqrt{x})^2} }\)

OpenStudy (solomonzelman):

my latex was not working sorry for the delay

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle \frac{ (x)'(1+\sqrt{x})-(x)(1+\sqrt{x})' }{(1+\sqrt{x})^2} }\) \(\large\color{black}{ \displaystyle \frac{ (1+\sqrt{x})-(x)(\frac{1}{2\sqrt{x}}) }{(1+\sqrt{x})^2} }\)

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle \frac{ 1+\sqrt{x}-\frac{\sqrt{x}}{2} }{(1+\sqrt{x})^2} }\)

OpenStudy (solomonzelman):

\(\large\color{black}{ \displaystyle \frac{ 1+\frac{2\sqrt{x}}{2}-\frac{\sqrt{x}}{2} }{(1+\sqrt{x})^2} }\) \(\large\color{black}{ \displaystyle \frac{ 1+\frac{\sqrt{x}}{2} }{(1+\sqrt{x})^2} }\)

OpenStudy (solomonzelman):

or, also \(\large\color{black}{ \displaystyle \frac{ 1+\frac{\sqrt{x}}{2} }{(1+\sqrt{x})^2} }\) \(\large\color{black}{ \displaystyle \frac{ \frac{2}{2}+\frac{\sqrt{x}}{2} }{(1+\sqrt{x})^2} }\) \(\large\color{black}{ \displaystyle \frac{ \frac{2+\sqrt{x}}{2} }{(1+\sqrt{x})^2} }\) \(\large\color{black}{ \displaystyle \frac{ 2+\sqrt{x}}{2(1+\sqrt{x})^2} }\) getting the exact same thing as the wolframalpha http://www.wolframalpha.com/input/?i=derivative+of+x%2F%281%2B%E2%88%9Ax%29

OpenStudy (solomonzelman):

do you understand what I did all throughout the thread ?

OpenStudy (anonymous):

Yes!! I finally got it!! Thank you! I figured out the part I kept getting wrong :)

OpenStudy (anonymous):

or you showed it to me lol

OpenStudy (solomonzelman):

:)

OpenStudy (solomonzelman):

I did a prove on the quotient using logarithmic differentiation, if you really want.

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