Calc II...

[bk12321 10+ year member]

I need some help on this problem...

Evaluate the integral: (integral) x(e^x) dx

read as the integral of x times e to the x dx

to start you guys off, set u = e^x and set a derivative dv=x dx

you get du = e^x and v=(x^2)/2

then you use the equation... the professor gave us this one

v * u - (integral) v * du

read as v times u minus the integral of v times du

I am just lost.. the professor did it this way but if I keep solving, I just get endless amounts of integrals that continue forever... so there has to be a way to do this.

thanks.

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[hemi=22s 10+ year member]

wtf //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[bk12321 10+ year member]

wtf //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif:crazy:

 

[duece212 5,000+ posts]

I need some help on this problem...
Evaluate the integral: (integral) x(e^x) dx

read as the integral of x times e to the x dx

to start you guys off, set u = e^x and set a derivative dv=x dx

you get du = e^x and v=(x^2)/2

then you use the equation... the professor gave us this one

v * u - (integral) v * du

read as v times u minus the integral of v times du

I am just lost.. the professor did it this way but if I keep solving, I just get endless amounts of integrals that continue forever... so there has to be a way to do this.

thanks.

Motherfukr I'm glad I dropped outta college while I was taking Calc 2

That sucks

 

[dragnix 5,000+ posts]

i hate u, i'm gonna go into engineering soon. I am not looking forwward to this shiz

 

[bk12321 10+ year member]

i hate u, i'm gonna go into engineering soon. I am not looking forwward to this shiz

calc I is easy, and if u pay attention and keep up with it, calc II isnt bad so far but ive heard it gets worse...

i already did a quarter of the problem at the top, it really isnt so bad, i just need to know what to do

 

[youngfu 10+ year member]

omg... only after 2 years out of college I completly forgot how to solve it... how idiot

 

[bk12321 10+ year member]

Motherfukr I'm glad I dropped outta college while I was taking Calc 2
That sucks

My friend is a complete genius... aces all classes and before he even got to college had college credit for 3 physics classes and pre calc and calc I

he got to calc II and now hes back at home going to some community college.. he dropped out lol

 

[ToyTundra 10+ year member]

set u =x, dv=e^x that way du =1 which simplifies it.

 

[bk12321 10+ year member]

set u =x, dv=e^x that way du =1 which simplifies it.

rgr that I just looked on cramster and thats what they say to do

so u = x du = 1 dv = e^x dx and v=e^x

so in the formula...

(x)(e^x)-(integral)(e^x) = xe^x - e^x

yessssssss hopefully thats right

 

[goofyre 10+ year member]

I'm in calc 1 and its hard as hell... stupid engineering //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[bk12321 10+ year member]

gangsteerrrrrrr

can anyone confirm that my answer is right??

xe^x - e^x

 

[bk12321 10+ year member]

I'm in calc 1 and its hard as hell... stupid engineering //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

ull probably think this is weird... but i found calc I really interesting

like i really paid attention in class cuz i wanted to learn how to do the shit

 

[ToyTundra 10+ year member]

gangsteerrrrrrr
can anyone confirm that my answer is right??

xe^x - e^x

+c if it's not evaluated

That sounds right. There should be a table of integrals in the back of your book (or online). The one you just did is a classic so it will for sure be there.

 

[LinxuS 10+ year member]

gangsteerrrrrrr
can anyone confirm that my answer is right??

xe^x - e^x + C

Yes, that's correct.

If you want to check, just take the derivative of what you just took the anti derivative of..

d/dx (xe^x - e^x + C) = e^x + x e^x - e^x

the e^x cancels out, leaving you xe^x