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![[Post New]](/templates/default/images/icon_minipost_new.gif) 6 Feb 2008 21:32:25 IST
Accepted Answer [?]
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(x-x1)(x-x2)......(x-xn) = x^n+x^(n-1)+......+1
take log...
log(x-x1) + log (x-x2) +.....log(x-xn) = log(x^n+x^(n-1)+...+1)
now differentiate both sides...
1/x-x1 + 1/x-x2 +..+1/x-xn = nx^(n-1)+(n-1)x^(n-2)+...+1 /(x^n+x^(n-1) +...+1)
put x=1...
required value = (1+ 2 +...+n )/ (1+1+....+1) --->n+1 times
so required value = n/2 (using 1+2+....+n = n(n+1)/2)
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this reply: 10 points
(with 2 
in 2 votes ) [?]
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