IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: crucio on October 22, 2009, 04:37:09 pm

Title: further math question...
Post by: crucio on October 22, 2009, 04:37:09 pm: $I_n = \displaystyle\int^1_0 x^n e^{-ax}\,dx \Rightarrow$ $\alpha I_n =nI_{n-1} - e^{-\alpha}$

find the Y coordinate of the centroid of the finite region bounded by the x-axis,
the line x = 1 and the curve $y=xe^{-x}$ , giving your answers in terms of e.

ans: $\dfrac{e^2 -5}{8e(e-2)}$

dunno how 2 arrive at da correct ans, i took $\alpha$ as 2 for $I_2$ but still im not gettin correct value...

ne help wud b highly appreciated...Thanks ::)
Title: Re: further math question...
Post by: astarmathsandphysics on October 22, 2009, 07:02:48 pm: Will answer when i get home
Title: Re: further math question...
Post by: astarmathsandphysics on October 23, 2009, 10:15:34 am: Quite a tricky question. Am doing it now.
Title: Re: further math question...
Post by: astarmathsandphysics on October 23, 2009, 11:02:52 am: ttook an hour to do.
Title: Re: further math question...
Post by: Ghost Of Highbury on October 23, 2009, 01:09:07 pm: Quote from: astarmathsandphysics on October 23, 2009, 11:02:52 am
ttook an hour to do.

r u serious sir?

if so, man!!!....i'm gonna face some horrible time with further maths in A levels..

gonna prepare from the start..!!
Title: Re: further math question...
Post by: astarmathsandphysics on October 23, 2009, 01:51:05 pm: Yes it was a quaestion full of tricky algebra. I couldn't read the pages I wrote cos of all the corrections I made.
Title: Re: further math question...
Post by: crucio on October 25, 2009, 04:01:06 pm: thank you very much sir! ;D