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If a(1),a(2),a(3)(a(1)gt0) are three suc...

If `a_(1),a_(2),a_(3)(a_(1)gt0)` are three successive terms of a GP with common ratio r, the value of r for which `a_(3)gt4a_(2)-3a_(1)` holds is given by

A

`1ltrlt3`

B

`-3ltrlt-1`

C

`rgt3orrlt1`

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
C
Let `a_(1),a_(2),a_(3)` be first three consecutive terms of G.P. with common ratio r. Then, `a_(2)=a_(1)randa_(3)=a_(1)r^(2)`.
Now,
`a_(3)gt4a_(2)-3a_(1)`
`rArr" "a_(1)r^(2)gt4a_(1)r-3a_(1)`
`rArr" "r^(2)gt4r-3`
`rArr" "r^(2)-4r+3gt 0rArr(r-1)(r-3)gt0rArrrlt1 or rgt3`
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OBJECTIVE RD SHARMA ENGLISH-SEQUENCES AND SERIES-Chapter Test
  1. If a(1),a(2),a(3)(a(1)gt0) are three successive terms of a GP with com...

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  2. Let H(n)=1+(1)/(2)+(1)/(3)+ . . . . .+(1)/(n), then the sum to n terms...

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  3. Sum of the first n terms of the series 1/2+3/4+7/8+(15)/(16)+............

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  4. If A(1),A(2) are between two numbers, then (A(1)+A(2))/(H(1)+H(2)) is ...

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  5. If the (m+1)t h ,(n+1)t h ,a n d(r+1)t h terms of an A.P., are in G.P....

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  6. Given that n arithmetic means are inserted between two sets of numbers...

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  7. If a,b, and c are in G.P then a+b,2b and b+ c are in

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  8. If in a progression a1, a2, a3, e t cdot,(ar-a(r+1)) bears a constant...

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  9. If in an AP, t1 = log10 a, t(n+1) = log10 b and t(2n+1) = log10 c then...

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  10. Find the sum of the series: 1^2-2^2+3^2-4^2+.....-2008^2+2009^2.

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  11. If 4a^(2)+9b^(2)+16c^(2)=2(3ab+6bc+4ca)," where "a,b,c are non-zero nu...

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  12. If Sn denotes the sum of n terms of an A.P. whose common difference is...

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  13. The sides of a right angled triangle are in A.P., then they are in the...

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  14. Find the sum of all the 11 terms of an AP whose middle most term is 30...

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  15. The maximum sum of the series 20+19 1/3+18 2/3+ is 310 b. 300 c. 0320 ...

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  16. If three numbers are in G.P., then the numbers obtained by adding the ...

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  17. If p ,q ,r are in A.P., show that the pth, qth and rth terms of any G....

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  18. Let a,b,c be three positive prime number. The progrrssion in which sqr...

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  19. If 1/(b-a)+1/(b-c)=1/a+1/c , then (A). a ,b ,a n dc are in H.P. (B). a...

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  20. If three numbers are in H.P., then the numbers obtained by subtracting...

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  21. The first three of four given numbers are in G.P. and their last three...

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