Question 2

Mathematics Parabola Easy

If \( x^{2}=-16y \) is an equation of parabola then:$$\begin{aligned} \text{(A)} & \quad \text{directrix is } y=4 \\ \text{(B)} & \quad \text{directrix is } x=4 \\ \text{(C)} & \quad \text{co-ordinates of focus are } (0,-4) \\ \text{(D)} & \quad \text{co-ordinates of focus are } (-4,0) \\ \text{(E)} & \quad \text{length of latus rectum } = 16 \end{aligned}$$ choose correct option

(A) (A) and (E) only
(B) (B), (C) and (E) only
(C) (A), (C) and (E) only
(D) (B), (D) and (E) only
✓ Correct Answer: Option C Verified Solution

📘 Step-by-Step Solution & Detailed Explanation:

Explanation:

The given parabola is
\[ x^{2} = -16y \]

Standard form of a vertical parabola opening downwards is
\[ x^{2} = -4ay \]

Comparing, we get
\[ 4a = 16 \;\; \Rightarrow \;\; a = 4 \]

Key elements:

  • Vertex: \( (0,0) \)
  • Focus: \( (0,-a) = (0,-4) \)
  • Directrix: \( y = a = 4 \)
  • Length of latus rectum: \( 4a = 16 \)

\[ \therefore \;\; \text{Correct options are (A), (C), and (E).} \]

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