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Mathematics 11 Online
OpenStudy (anonymous):

Integrate!

OpenStudy (anonymous):

\[\displaystyle \int\limits_0^1 8^{3 x}\, dx\]

OpenStudy (anonymous):

lny = 3xln8

OpenStudy (dls):

Use the property \[\Huge \int\limits a^x = \frac{a^x}{\log a}\]

OpenStudy (anonymous):

(8^x)/log8 ?

OpenStudy (dls):

Put 3x=t

OpenStudy (dls):

So it becomes, \[\Huge \frac{1}{2}\int\limits_0^\frac{1}{2} 8^t dt\] Now shoot the property.

OpenStudy (dls):

sorry that would be 1/3 , i thought its 2x

OpenStudy (anonymous):

yeah

OpenStudy (dls):

\[\Huge \frac{1}{3}\int\limits\limits_0^\frac{1}{3} 8^t dt\] Can you do now?

OpenStudy (anonymous):

so then we get 8^t /(log8*3) eval at 1/3

OpenStudy (anonymous):

no thats wrong >.>

OpenStudy (anonymous):

oh snap, i know what i did

OpenStudy (dls):

\[\Large \frac{1}{3} \frac{8^t}{\log 8}]_0^\frac{1}{3}\]

OpenStudy (dls):

\[\Large \frac{1}{3} (\frac{2}{\log 8} - \frac{1}{\log 8})=> \frac{1}{3 \log 8}\]

OpenStudy (anonymous):

woah where did 2 -1 come from?

OpenStudy (dls):

\[\Huge 8^\frac{1}{3} = (2)^{3 \times \frac{1}{3}}\]

OpenStudy (dls):

and 8^0=1

OpenStudy (anonymous):

there we go, thats what i was missing... i was just dropping off the whole second part of the integral

OpenStudy (anonymous):

thank you

OpenStudy (dls):

haha be careful next time :)

OpenStudy (anonymous):

yeah the -1/log8 got me!

OpenStudy (anonymous):

@DLS we were still wrong it was evaluated at 3 and 0, instead of 1/3 and 0 the answer wasn't accepting so i redid it :p

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