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AP EAMCET · Maths · Quadratic Equation

If \(\alpha, \beta\) are the roots of \(x^2-3 x+a=0\) and \(\gamma, \delta\) are the roots of \(x^2-12 x+b=0\) and \(\alpha, \beta, \gamma, \delta\) in that order form a geometric progression in increasing order with common ratio \(r>1\), then \(a+b=\)

  1. A \(16\)
  2. B \(28\)
  3. C \(34\)
  4. D \(42\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(34\)

Step-by-step Solution

Detailed explanation

\(\alpha=k, \beta=kr, \gamma=kr^2, \delta=kr^3\) \(\alpha+\beta = k(1+r) = 3\) \(\gamma+\delta = kr^2(1+r) = 12\) \(\frac{kr^2(1+r)}{k(1+r)} = \frac{12}{3} \Rightarrow r^2=4 \Rightarrow r=2\) (since \(r>1\)) \(k(1+2)=3 \Rightarrow 3k=3 \Rightarrow k=1\)…
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