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Mathematics 7 Online
OpenStudy (earthcitizen):

int[p(1+p)^(1/2)]

OpenStudy (anonymous):

try \(u=1+p\)

OpenStudy (earthcitizen):

\[\int\limits p(1+p)^{1/2} dp\]

OpenStudy (earthcitizen):

u=1+p . du/dp = 1

OpenStudy (earthcitizen):

i'm suppose to use integration by parts but I 'm getting a funny answer

OpenStudy (anonymous):

parts? why not \[\int p(\sqrt{1+p})dp\] \[u=1+p, du=dp , p=u-1\] \[\int (u-1)\sqrt{u}du\] \[\int (u^{\frac{3}{2}}-u^{\frac{1}{2}})du\] etc

OpenStudy (earthcitizen):

i know, i want to use integration by parts not substitution

OpenStudy (anonymous):

ok so we want \(\int udv = uv-\int vdu\) what do we pick?

OpenStudy (earthcitizen):

not really sure, boss

OpenStudy (anonymous):

see i think it will come down to a u - sub using this method as well

OpenStudy (anonymous):

we could say \[u=p,dv = \sqrt{1+p}\] and then \[du=dp\] and \[v=\int\sqrt{1+p}dp\]

OpenStudy (earthcitizen):

yep

OpenStudy (anonymous):

i guess that will work because \[\int \sqrt{1+p}=2(1+p)^{\frac{3}{2}}\] of i am not mistaken

OpenStudy (earthcitizen):

kk, go on..

OpenStudy (anonymous):

so putting it together we get \[uv-\int v du =2p(1+p)^{\frac{3}{2}}-\int 2(1+p)^{\frac{3}{2}}dp\] let me know if i messed up

OpenStudy (earthcitizen):

\[2/3(1+p)^{3/2}\]

OpenStudy (anonymous):

yeah right i forget the 3 in the denominator

OpenStudy (anonymous):

\[uv-\int v du =\frac{2}{3}p(1+p)^{\frac{3}{2}}-\frac{2}{3}\int (1+p)^{\frac{3}{2}}dp\]should be better

OpenStudy (earthcitizen):

yh

OpenStudy (anonymous):

and the last one is ok by power rule, get \[-\frac{3}{2}\int(1+p)^{\frac{3}{2}}dp=-\frac{15}{4}(1+p)^{\frac{5}{2}}\] unless i messed up again

OpenStudy (anonymous):

no i messed up again

OpenStudy (anonymous):

these \(p\)'s are getting on my nerves. what is wrong with \(x\)?

OpenStudy (earthcitizen):

lol

OpenStudy (anonymous):

\[-\frac{2}{3}\int(1+p)^{\frac{3}{2}}dp=-\frac{4}{15}(1+p)^{\frac{5}{2}}\]

OpenStudy (anonymous):

there i think that is correct now

OpenStudy (earthcitizen):

yh, prolly

OpenStudy (anonymous):

first method is clearly snappier

OpenStudy (earthcitizen):

kk, how do we wrap it up nicely by factorisation ? coz from what we did i got\[2/3[p(1+p)^{3/2}-2/5[(1+p)^{5/2}] +c\]

OpenStudy (anonymous):

i will leave that up to you, because i have to bolt

OpenStudy (earthcitizen):

hehe, no p. Thanks you, Master Shifu

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