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AP EAMCET · Maths · Parabola

If the directrix of the parabola \(x^2+4 y-6 x+\lambda=0\) is \(y+1=0\), then which of the following is correct?

  1. A \(\lambda=-17\)
  2. B \(\lambda=-19\)
  3. C focus is \((3,-3)\)
  4. D vertex is \((3,-3)\)
Verified Solution

Answer & Solution

Correct Answer

(C) focus is \((3,-3)\)

Step-by-step Solution

Detailed explanation

Parabola is \((x-3)^2=-4\left(y-\left(\frac{\lambda-9}{4}\right)\right)\) Equation of direction is \(y=\frac{\lambda-9}{4}+1\) \(\therefore\) As direction is \(y+1=0, \frac{\lambda-9}{4}+1=-1\) \(\lambda=1\) \(\therefore\) Vertex is \((3,-2)\) and focus is \((3,-3)\).