∫ 0 ∞ ( x 2 + 1 x ) 5 [ ln ( x 2 + 1 x ) ] x 2 d x = − B A
If the equation above holds true for coprime positive integers A , B , , find B − A − 1 0 4 .
this is a part of Who's up to the challenge?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
i've edited the problem :)
Log in to reply
But why ask for an answer which does not use B?
Log in to reply
i'll include B
How about now?
I got the solution but couldnt answer it in the given form. You should make the changes earlier. Points lost 😭 Btw, you post nice problems!
Problem Loading...
Note Loading...
Set Loading...
The integral is equal to F ′ ( 5 ) , where F ( a ) = ∫ 0 ∞ ( x 2 + 1 ) a x a − 2 d x = 2 1 ∫ 0 ∞ ( 1 + u ) a u 2 1 ( a − 1 ) d a = 2 1 B ( 2 1 ( a − 1 ) , 2 1 ( a + 1 ) ) and so F ′ ( 5 ) = F ( 5 ) [ 2 1 ψ ( 2 ) + 2 1 ψ ( 3 ) − ψ ( 5 ) ] = 2 4 1 [ 2 1 H 1 + 2 1 H 2 − H 4 ] = 2 4 1 [ H 2 − H 4 − 4 1 ] making the answer 2 + 4 + 1 + 4 + 2 4 = 3 5 , but why give the answer like this? The quantity F ′ ( 5 ) is equal to − 1 4 4 5 . You could even keep the answer the same by saying that the integral is of the form − B A where A , B are coprime integers, and ask for A B + 3 1 (or something similar) as the answer.