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Mathematics 20 Online
OpenStudy (anonymous):

integrate x^33^x dx

OpenStudy (anonymous):

product of x raised to power three and 3 raised to power x

OpenStudy (anonymous):

i assume this is \[\int x^33^xdx\]

OpenStudy (anonymous):

ya

OpenStudy (anonymous):

it is a set up for integration by parts, but you have to do it 3 times ! will reduce the power on \[x^3\] once each time

OpenStudy (anonymous):

i have assumed f(x)=x^3 and g'(x)=3^x

OpenStudy (anonymous):

for example in the first time you will put \[u=x^3, dv=3^xdx, du=3x^2,v=\frac{3^x}{\ln(3)}\] and get \[uv-\int vdu=\frac{x^33^x}{\ln(3)}-\frac{3}{\ln(3)}\int x^23^xdx\]

OpenStudy (anonymous):

then lather, rinse, repeat. hold on

OpenStudy (anonymous):

easier to read it , click "show steps" http://www.wolframalpha.com/input/?i=x^3*3^x+dx

OpenStudy (anonymous):

how would u integrate 3x^2.3^x/log3

OpenStudy (anonymous):

first of all pull out the constants like i did above and get \[-\frac{3}{\ln(3)}\int x^23^xdx\] then repeat the parts, this time with \[u=x^2\]

OpenStudy (anonymous):

ur ans went over my head

OpenStudy (anonymous):

ok it is confusing, but if you got the first one right you should have a good idea what is going on each time you integrate by parts, you will reduce the power by one when you take the derivative of \[x^3, x^2, x\]

OpenStudy (anonymous):

don't forget that \[\ln(3)\] is a number (constant) so it come right out front of the integral sign

OpenStudy (anonymous):

your next job is really \[\int x^2 3^xdx\] the constant just sits out front. integrate by parts again

OpenStudy (anonymous):

let me show u the first step......3x^2.3x/log3-integrate3x^2.3^x/log3 dx

OpenStudy (anonymous):

ah first step is wrong that is the problem

OpenStudy (anonymous):

it is \[\int udv=uv-\int vdu\]

OpenStudy (anonymous):

i dnt use that formula

OpenStudy (anonymous):

\[u=x^3,du = 3x^2, dv = 3^x, v = \int 3^x=\frac{3^x}{\ln(3)}\]

OpenStudy (anonymous):

\[uv=\frac{x^33^x}{\ln(3)}\]

OpenStudy (anonymous):

and i stress again, even though the second one is \[-\int \frac{3x^23^x}{\ln(3)}dx\] you should rewrite it immediately as \[-\frac{3}{\ln(3)}\int x^23^xdx\]

OpenStudy (anonymous):

i m having trouble with the formula implementation......wht to do?

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