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AlgebraEasyEquation of a horizontal line

Algebra practice question

Which of the following is an equation of a horizontal line in the xy-plane?

  1. A. y = 3Correct
  2. B. x = 3
  3. C. y = x
  4. D. y = 3x

Answer: A. y = 3

y = 3 keeps y fixed for every x: a horizontal line.

Why the other answers are wrong

B. x = 3
x = 3 is vertical.
C. y = x
y = x rises at 45°.
D. y = 3x
y = 3x is a sloped line through the origin.

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