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Topic: Need help on maths

Ok doing A level maths... this is level 3 calculus (c3)... the only thing im not 100% on so far...

ok so its intergration i aint sure how to integrate this..

i cant do the intergration sign on this forum so ill assume you can guess its there :

  _
|    2
|     x^2 lnx dx        give your answer in an exact form.
|_  1


any help would be appreciated smile x

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Re: Need help on maths

i need to be able to answer it for my college course tongue

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Re: Need help on maths

You're answer is 3.

Your = possessive. As in, "your grammar sucks."
You're = you are. As in, "you're an idiot for not knowing the difference."

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Re: Need help on maths

i have the questions and the answers.. but that wont do me any good in the exam i need to understand how to answer the question.. im ill atm so cant get to school so was hoping one of you guys would be able to help..

cmon must be a maths geek out there somewhere?! tongue

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Re: Need help on maths

oh and its not 3 tongue x

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Re: Need help on maths

Integration by parts with a wrap-around function I believe. I'll look more after class maybe

Never attribute to malice that which is adequately explained by stupidity.

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Re: Need help on maths

the way i started attempting it was

i let u = ln x

and i let dv/dx = x^2   

so therefore v = 1/3x^3


from here i got stock.. unsure what part to put where and which part to do first.. i did a few attempts but couldnt get the right answer..

perhaps my start is wrong..

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Re: Need help on maths

Ask Flint.

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Re: Need help on maths

As long as he doesnt try and pretend he invented integration i dont mind who helps me smile x

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Re: Need help on maths

Like TR said, use integration by parts:

x^2 goes to 1/3x^3
lnx goes to xln(x)-x

as an equation it looks like:    2
[1/3x^3ln(x) + x^2.xln(x)-x]
                                           1



Pretty sure that's right anyway. If it's not someone will gleefully correct me I'm sure tongue

<Mizzle> ive been in a jailcel for the first time of my life during this night lol
<Mizzle> new experience big_smile

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Re: Need help on maths

Oh, and the answer is 0 yes?

<Mizzle> ive been in a jailcel for the first time of my life during this night lol
<Mizzle> new experience big_smile

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12 Reply by Destroyyoutoo|SDChampion0 (edited by Destroyyoutoo 03-Dec-2009 03:55:02)

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Re: Need help on maths

Humidity:

u*v- integral(du*v)

So make your u = ln(x)

Make dv = x^2



Then you have:

ln(x)*x^3/3 - integral( (1/x)*x^3/3))

Evaluate your new integral, its simple, then solve it from 2 to 1, you're in calc 3 so I'm guessing you can do that.  Tell us if you get stuck.

TR noticed I screwed up the integration and he was right.  I changed it.

TC pwns me

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Re: Need help on maths

ur all wrong...

the answer is

1+1 = 3

Yes!

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Re: Need help on maths

yeah no wrap around. dyt is correct

Never attribute to malice that which is adequately explained by stupidity.

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Re: Need help on maths

for the record, where are you from humidity?

in the us this is not calc 3, only calc 2. proof that we are smarter X(

Never attribute to malice that which is adequately explained by stupidity.

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Re: Need help on maths

He's in the UK, prolly 17/18. Pre-university.

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Re: Need help on maths

He prolly still poops his pants

<@Nolio> Ilu was the man back in the day,he even made monkeywrench and arganon look good for half a round =p
<@iluvatar> it is my grandest achievement
<@Nolio> *half a round  =p
<@iluvatar> still
* Final_Doom is now known as Thanks_Iluvatar

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Re: Need help on maths

ahh got it now thanks guys..

Yeah i missed this being taught through illness.. i was gonna teach myself but i got pwned at first.. think im starting to understand it.. test in a month ahh..

oh and yeh arfeh is correct.. im 17 in uk.. and im pre-uni tongue x

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Re: Need help on maths

zomg, yoou dont really grow up fast do you humi tongue?


when in doubt, the answer is 42, of course

till the end of time..

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