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Let a₁, a₂, a₃, be a G.P. of increasing positive terms. If a₁ a₅=28 and a₂+a₄=29 , then a₆ is equal to:

Options

  1. A628
  2. B812
  3. C526
  4. D784

Correct answer

D. 784

Step-by-step solution

aligned & a₁ a₅=28 a^2 r^4=28 & a₂+a₄=29 a r+a r^3=29 aligned ar and a r^3 are roots of aligned & k^2-29 k+28=0 & k=1, k=28 & a r=1, a r^3=28 & r^2=28, a^2= 1 28 & a₆=a r^5 r^4=28^2 & a₆=784 aligned

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