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AlgebraMediumWhich equation has a given slope and passes through a point

Algebra practice question

Which equation represents a line with slope −3 that passes through the point (1, 4) in the xy-plane?

  1. A. y = −3x + 7Correct
  2. B. y = −3x + 4
  3. C. y = −3x + 1
  4. D. y = 3x + 1

Answer: A. y = −3x + 7

y = −3x + b with 4 = −3(1) + b gives b = 7.

Why the other answers are wrong

B. y = −3x + 4
b = 4 uses the point's y-coordinate as the intercept; that works only if x = 0.
C. y = −3x + 1
y = −3x + 1 gives −2 at x = 1.
D. y = 3x + 1
The slope is +3, the wrong sign.

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