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?

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. $\lambda=-17$
  2. $\lambda=-19$
  3. focus is $(3,-3)$
  4. vertex is $(3,-3)$

Solution

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 $(3,-3)$.

Asked in: AP EAMCET 2022 (07 Jul Shift 2)

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