If the value of the integral above equals , where is a positive integer, find .
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We can write the above Integral as an integral of an infinite series,like so:
∫ 0 1 ( ln x ) 2 ( 1 − x ) − 2 d x = ∫ 0 1 ( ln x ) 2 ( 1 + 2 x + 3 x 2 + 4 x 3 . . . . . . ) d x
A general form would be ,
I = ∑ r = 0 ∞ ∫ 0 1 ( l n x ) 2 ( r + 1 ) x r d x
now I ( m , n ) = ∫ 0 1 x m ( l n x ) n d x = ( m + 1 ) n + 1 ( − 1 ) n n !
The derivation of the above expression is part of the solution of an amazing and very similar problem by Ishan Tarunesh,here's the link: Off the charts!
Therefore, On solving further
∑ r = 0 ∞ ( r + 1 ) ( r + 1 ) 2 + 1 ( − 1 ) 2 2 ! = 2 ∑ r = 0 ∞ ( r + 1 ) 2 1 = 3 π 2
And so a = 2