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Which of the following describes the equation of a line that crosses the x-axis when x = -4 and has a negative slope?

(A) y = 5x + 20
(B) y = -5x - 20
(C) y = -5x + 20
(D) y = 5x - 4
(E) y = -5x - 4

1 Answer

3 votes

Final answer:

The equation of a line that crosses the x-axis at x = -4 with a negative slope is given by option (C) y = -5x + 20, which is the only equation that meets both criteria.

Step-by-step explanation:

When determining the equation of a line that crosses the x-axis at a specific point and has a certain slope, we should look for two characteristics in the equation: the x-intercept and the slope. The x-intercept is the value of x where the line crosses the x-axis, and the slope indicates the steepness of the line and whether it rises or falls as it moves from left to right on a graph.

In this case, we are looking for a line that crosses the x-axis when x = -4 and has a negative slope. A negative slope means that as we move from left to right, the line goes downward. Given these criteria, let's evaluate the options provided:

  • (A) y = 5x + 20: This has a positive slope and is therefore not correct.
  • (B) y = -5x - 20: This has a negative slope, but it would cross the x-axis at x = 4, not x = -4.
  • (C) y = -5x + 20: This option has a negative slope and crosses the x-axis at x = -4 because if you set y=0 to find the x-intercept, x indeed equals -4. Thus, this is the correct equation.
  • (D) y = 5x - 4: Positive slope, incorrect.
  • (E) y = -5x - 4: Negative slope but incorrect x-intercept.

Therefore, the correct option, based on the given information, is (C) y = -5x + 20.

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