0 ∫ ∞ ( 1 0 x 9 + 8 ) 7 x 6 d x
Given the above integral can be expressed as D E G F H G I Γ ( B A ) Γ ( B C ) where A , B , C , D , E , F , G , H , I all are positive integers.
Find the value of A + B + C + D + E + F + G + H + I .
Details and Assumptions:
1) g cd ( A , B ) = g cd ( C , B ) = g cd ( F , G ) = g cd ( I , G ) = 1
2) Here Gamma functions may or may not be reducable. For more clarity 0 < B A < 1 and B C > 1
3) Also G F < 1 and G I < 1
4) E and H are prime numbers.
Inspiration - Caboodle of Tricks .
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@Aman Raimann Kindly change that d in your problem to some more variable like what I have given. That d makes the problem relatively boring. An answer like 3 3 9 7 3 8 6 3 3 9 is just not interesting, make it smaller. Please edit.
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yaaa. but i cant chnge the answer now...
what is gamma function
Y did u post the solution! (just kidding) I'm a newbie in RMT and even I did the same way.
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I will prove a general integral -
∫ 0 ∞ ( b + c x d ) e x a d x = Γ ( e ) d b e − d a + 1 c d a + 1 Γ ( d a + 1 ) Γ ( e − d a + 1 )
I will do this using a more non-conventional way using Ramanujan Master Theorem .
Substituting u = b c x d , d x = c d x d − 1 b d u
c d b e b ∫ 0 ∞ ( 1 + u ) e x a − d + 1 d u
c d b e − 1 1 ∫ 0 ∞ ( 1 + u ) e ( c b u ) d a − d + 1 d u
d c d a + 1 b e − d a + 1 1 ∫ 0 ∞ ( 1 + u ) e u d a + 1 − 1
Now the last integral is in the form of Mellin transform, so, we will use Ramanujan Master Theorem. We know that
( 1 + x ) n 1 = k = 0 ∑ ∞ Γ ( n ) Γ ( n + k ) k ! ( − x ) k
We get that our last integral will be equal to -
Γ ( d a + 1 ) Γ ( e − d a + 1 )
Hence our total integral becomes -
Γ ( e ) d b e − d a + 1 c d a + 1 Γ ( d a + 1 ) Γ ( e − d a + 1 )
QED
Actually, the most difficult part of the problem is not what I have done. It's the calculations which follow.