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Reviewed CSCA Mathematics question · Hard

What is the length of the latus rectum of the parabola given by the equation y^2 = -12x?

  1. 12
  2. 6
  3. 24
  4. 3
Show the answer and explanation

Correct answer

A. 12

Principle or equation

For a parabola of the form y^2 = 4px, the length of the latus rectum is |4p|.

Why this answer is correct

The equation y^2 = -12x can be written as y^2 = 4(-3)x, so p = -3. The length of the latus rectum is |4p| = |-12| = 12.

Example

For y^2 = 8x, p = 2, latus rectum = 8.

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