same as tht of above guy..but considering "giving solns"..wic is really amazing..
the expression inside tht sumation wen simplified gives.. 2^n + {2^(n+1) - 1}/n+1..now tht is equal to ur 2^8 - 1 / 6..
the rhs misses a factor of 2..by tht i mean 2 is left below it..
similarly lhs shud have have one 2 missing out..
solving lhs..{ n.2^n + 2^n + 2^(n+1) -1..} /n+1... ur numerator has zero exponent of 2..(it is obviously odd).. so n+1 is having 2's exponent as 1.. so next task is to find tht n.. numerator in rhs is 21.. so (n+2)(2^n +1) = 24 (as n+1 is even).. n+2 is definitely odd.. 2^n +1 is odd ! so no soln..
Diamonds r formed under greatest pressures..
so r the champs.
Moderation Team
![[Post New]](/templates/default/images/icon_minipost_new.gif){kind=icon}
![[Up]](/templates/default/images/icon_up.gif "[Up]"){kind=icon}
26
![\displaystyle\sum_{r=0}^{n}\left[ \frac {r+2}{r+1} \right] .^nC_r=\frac{2^8-1}{6}](http://alt1.artofproblemsolving.com/Forum/latexrender/pictures/4/8/8/4883fbff0431c2fc5d7322e2d5ac05784795ba63.gif)
,then n is equal to ??
