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AlgebraEasyEquation of a line with slope 1 through the origin

Algebra practice question

Which of the following equations describes the line in the xy-plane on which every point has a y-coordinate equal to its x-coordinate?

  1. A. y = xCorrect
  2. B. y = −x
  3. C. y = 1
  4. D. x + y = 1

Answer: A. y = x

y = x is exactly the condition that y equals x.

Why the other answers are wrong

B. y = −x
y = −x gives opposite signs.
C. y = 1
y is fixed at 1.
D. x + y = 1
The coordinates add to 1.

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