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Reviewed CSCA Mathematics question · Standard

What is the length of the latus rectum of the parabola given by the equation x^2 = -8y?

  1. 8
  2. 4
  3. 16
  4. 2
Show the answer and explanation

Correct answer

A. 8

Principle or equation

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

Why this answer is correct

The equation x^2 = -8y can be written as x^2 = 4(-2)y, so 4p = -8, hence |4p| = 8. The latus rectum length is 8.

Example

For y^2 = 12x, 4p = 12, so latus rectum length is 12.

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