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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)
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  3. If the coefficient of the rth, (r+1)th and (r+2)th terms in the expans...

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  4. If the coefficient of x^(7)in [ax^(2) + (1/bx)]^(11) equals the coeffi...

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  5. For natural numbers m ,n ,if(1-y)^m(1+y)^n=1+a1y+a2y^2+... , and a1=a2...

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

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  7. The sum of series .^(20)C0-^(20)C1+^(20)C2-^(20)C3+....+^(20)C 10 is

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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 reamainder left out when 8^(2n) - (62)^(2n+1) is divided by 9 is

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  10. For r = 0, 1,"…..",10, let A(r),B(r), and C(r) denote, respectively, t...

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  11. Let S(1) = sum(j=1)^(10) j(j-1).""^(10)C(j), S(2) = sum(j=1)^(10)j."...

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

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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. The term independent of x in expansion of ((x+1)/(x^(2/3)-x^(1/3)+1)-(...

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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 coefficient of x^(3) and x^(4) in the expansion of (1+ax+bx^(2)...

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

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  18. The sum of coefficient of integral powers of x in the binomial expansi...

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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 ne 0,...

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