1. cr2 + (2c – b2)r + c = 0
  2. cr2 + (2c + b2) + c = 0
  3. c2r2 + (2a - b2) + c = 0
  4. c2r2 + (2a + b2) + c = 0
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1 Answers

Option 1 : cr2 + (2c – b2)r + c = 0

Let the roots which are in geometric progression be a and ar

here, r is called as common ratio

⇒ a + ar = - b (sum of roots = -b)

⇒ a(1 + r) = - b

⇒ a = -b/(1 + r)

⇒ a × ar = c ( product of roots = c)

⇒ a2r = c

⇒ (- b/(1 + r))2 r = c

⇒ b2r = c + cr2 + 2cr

⇒ cr2 + (2c – b2)r + c = 0

∴ option 1 is correct
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