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Mathematics 18 Online
OpenStudy (anonymous):

Integrate by parts. See below.Need help as to process.

OpenStudy (anonymous):

\[\frac{ x }{ \sqrt{5+4x} }dx\]

OpenStudy (anonymous):

Let u =x and dv = (5+4x)^(-1/2) dx

OpenStudy (anonymous):

I did that

OpenStudy (anonymous):

So the anti derivative of (5+4x)^(-1/2)is 2(5+4x)^1/2?

OpenStudy (anonymous):

yup

OpenStudy (anonymous):

Hold on

OpenStudy (anonymous):

1/2 not 2 in the front. hehehe

OpenStudy (anonymous):

Sorry why 1/2?

OpenStudy (anonymous):

Is it 2 divided by 4 because of the 4x?

OpenStudy (anonymous):

\[\int \dfrac{1}{\sqrt{5+4x}}dx\] let u = 5+4x --> du = 4dx--> dx = du/4 \[\int \dfrac{1}{\sqrt{5+4x}}dx =\dfrac{1}{4}\int u^{-1/2} du = \dfrac{1}{4}*2\sqrt u= \dfrac{1}{2}\sqrt{5+4x} \]

OpenStudy (anonymous):

So that would become \[\frac{ 2 }{ 9 }(5+4x)^{3/2}\]

OpenStudy (anonymous):

Soory not 4/9 but 1/3

OpenStudy (anonymous):

that is v, right? so that you have u = x dv = ... du = dx v = \(\dfrac{1}{2}\sqrt {5+4x}\) now combine to get \(uv -\int vdu\)

OpenStudy (anonymous):

\[2x*(5+4x)^{1/2}-1/3(5+4x)^{3/2}+C\]

OpenStudy (anonymous):

ok, let check by wolfram http://www.wolframalpha.com/input/?i=int+%28x%2F%28sqrt%285%2B4x%29%29dx

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