Question

Select the correct option from the given alternatives:

If the focus of the parabola is (0, –3) its directrix is y = 3 then its equation is

Options

• x² = – 12y

• x² = 12y

• y² = 12x

• y² = −12x

Answer 1

x² = – 12y

Explanation;

SP² = PM²

∴ (x – 0)² + (y + 3)² = `|(y - 3)/sqrt(1)|^2`

∴ x² + y² + 6y + 9 = y² – 6y + 9

∴ x² = – 12y