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Sum of first 20 terms of 3/1^2 + 5/(1^2...

Sum of first 20 terms of ` 3/1^2 + 5/(1^2 + 2^2) + 7/(1^2 + 2^2 + 3^2) `+... upto 20 terms is :

A

120

B

180

C

240

D

60

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The correct Answer is:
A
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DISHA PUBLICATION-SEQUENCES AND SERIES -Exercise -2 : Concept Applicator
  1. Sum of first 20 terms of 3/1^2 + 5/(1^2 + 2^2) + 7/(1^2 + 2^2 + 3^2) ...

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  2. If a(1), a(2), …..,a(n) are in A.P. with common difference d ne 0, the...

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  3. If 1,log9(3^(1-x)+2), log3(4*3^x-1) are in A.P then x equals to

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  4. In the coefficients of rth, (r+1)t h ,a n d(r+2)t h terms in the binom...

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  5. The minimum value of (x^4+y^4+z^2)/(x y z) for positive real numbers x...

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  6. If every even term of a series is a times the term before it and every...

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  7. If y=3^(x-1)+3^(-x-1) (where, x is real), then the leastvalue of y is

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  8. Let a1, a2, a3, ...an be an AP. Prove that: 1 / (a1 an) + 1 / (a2 a(n-...

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  9. Concentric circles of radii 1,2,3,. . . . ,100 c m are drawn. The inte...

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  10. If log(e)5, log(e)(5^(x) -1) and log(e)(5^(x)-(11)/(5)) are in A.P the...

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  11. If a ,b ,c are the sides of a triangle, then the minimum value of a/(b...

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  12. The value of 1/(2!) +2/(3!) +...+999/(1000!) is equal to

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  13. If a,b,c are in H.P.then which one of the following is true

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  14. If a,b,c and the d are in H.P then find the vlaue of (a^(-2)-d^(-2))/(...

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  15. The odd value of n for which 704 + 1/2 (704) + 1/4 (704) + ... upto n ...

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  16. If (1-p)(1+3x+9x^2+27 x^3+81 x^4+243 x^5)=1-p^6p!=1 , then the value o...

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  17. The harmonic mean of (a)/(1 - ab) and (a)/(1 + ab) is :

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  18. The sum of the infinite series(2^(2))/(2!) + (2^(4))/(4!) + (2^(6))/(6...

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  19. If a,b,c re in H.Pthen which one of the following is true

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  20. ABC is a right angled triangle in which /B=90^(@) and BC=a. If n point...

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  21. If S(1), S(2), S(3),...,S(n) are the sums of infinite geometric series...

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