Question

If focal chord of the parabola y² = ax is 2x – y – 8 = 0 then the equation of directrix is

• A. x + 4 = 0
• B. x – 4 = 0
• C. y – 4 = 0
• D. y + 4 = 0

Answer 1

Answer: (A)

x + 4 = 0

Answer 2

Since focal chord of parabola y² = ax is

2x – y – 8 = 0, so the chord will pass through the focus

$\left( \frac{a}{4},0 \right)$

\ 2$\left( \frac{a}{4} \right)$– 0 – 8 = 0 \ a = 16

\ directrix x + 4 = 0