Mathematics
11 Online
OpenStudy (anonymous):
Integrate!
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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
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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
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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?
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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 :)
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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