Question

The coordinates of a point on the parabola y² = 8x, whose focal distance is 4, are

• A. $\left( \frac { 1 } { 2 } , \pm 2 \right)$
• B. (1, ± 2√2)
• C. (2, ± 4)
• D. None

Answer 1

Answer: (C)

(2, ± 4)

Answer 2

If the coordinates of a point on the parabola y² = 4ax are

P(x,y), then its focal distance is SP = x + a.

Here a = 2 and SP = 4.

4 = x +2 ⇒ x = 2 ⇒ y² = 8x2 ⇒ y = ± 4.

Hence (3) is the correct answer.