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Find the sum of sum(r=1)^n(r^n Cr)/(^n C...

Find the sum of `sum_(r=1)^n(r^n C_r)/(^n C_(r-1)` .

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Verified by Experts

`because (r.""^(n)C_(r))/(r.""^(n)C_(r-1))= (n-r +1)/(r) `
` therefore (r.""^(n)C_(r))/(r.""^(n)C_(r-1))= (n-r +1) `
`therefore sum_(r=1)^(n) (r.""^(n)C_(1))/(r.""^(n)C_(r-1)) = sum_(r=1)^(n) (n-r+1)= sum_(r=1)^(n) (n+1) -sum_(r=1)^(n)r `
` =(n+1).n-(n(n+1))/(2) = (n(n+1))/(2)`
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ARIHANT MATHS-BIONOMIAL THEOREM-Exercise (Questions Asked In Previous 13 Years Exam)
  1. Find the sum of sum(r=1)^n(r^n Cr)/(^n C(r-1) .

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  2. The value of (30 0)(30 10)-(30 1)(30 11)+(30 2)(30 12)++(30 20)(30 30)...

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  3. If the coefficient of pth, (p+1)thand (p+2)th terms in the expansion ...

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  4. If the coefficient of x^7 in (ax^2+1/(bx))^11 is equal to the coeffici...

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  5. For natural numbers m ,n ,if(1-y)^m(1+y)^n=1+a1y+a2y^2+ ,a n da1=a2=10...

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  6. In the binomial expansion of (a - b)^(n) , n ge 5 , the sum of the ...

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  7. The sum of the series C 20()0-C 20()1+C 20()2-C 20()3+...-...+C 20()(1...

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  8. Statement-1: sum(r =0)^(n) (r +1)""^(n)C(r) = (n +2) 2^(n-1) Stat...

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  9. The remainder left out when 8^(2n)""(62)^(2n+1) is divided by 9 is (1)...

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  10. For r= 0, 1,.....,10, let Ar,Br, and Crdenote, respectively, the coe...

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  11. So, statement-1 is also true. Stetement-2 is a correct expanation fo...

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  12. The coefficient of x^(7) in the expansion of (1-x-x^(2) + x^(3))^(6) i...

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  13. If n is a positive integer, then (sqrt(3)+1)^(2n)-(sqrt(3)-1)^(2n) is ...

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  14. In the expansion of ((x+1)/(x^(2/3)-x^(1/3)+1)-(x-1)/(x-x^(1/2)))^10 ...

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  15. The coefficients of three consecutive terms of (1+x)^(n+5) are in the ...

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  16. If the coefficients of x^(3) and x^(4) in the expansion of (1 + ax + b...

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  17. Coefficient of x^(11) in the expansion of (1+x^2)(1+x^3)^7(1+x^4)^(12)...

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  18. The sum of coefficients in integral powers of x in the binominal expan...

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  19. The coefficient of x^9 in the expansion of (1+x)(16 x^2)(1+x^3)(1+x^(1...

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  20. If the number of terms in the expansion of (1-2/x+4/(x^2))^n , x!=0, i...

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  21. Let m be the smallest positive integer such that the coefficient of x^...

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