A linear equation is graphed on the coordinate plane below.

The graph shows a coordinate grid with a straight line that passes through the points (negative 9, negative 5), (negative 6, negative 4) (negative 3, negative 3), (0, negative 2), (3, negative 1), (6, 0), and (9, 1).

When graphed on the same coordinate plane, which equation results in a system of equations with exactly one solution?

A. -2x + 6y = -12

B. 3x - 9y = 9

C. x - 3y = 6

D. 9x - 3y = 6

1 answer

To determine which equation will result in a system with exactly one solution, we need to find an equation that represents a line that is not parallel to the given linear equation on the graph.

  1. Identify the slope of the given line: The points provided can help us find the slope. Let's take two points, for example, (0, -2) and (3, -1).

    Slope (m) can be calculated as: \[ m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{-1 - (-2)}{3 - 0} = \frac{1}{3} \]

    The slope of the line is \( \frac{1}{3} \).

  2. Determine the slopes of the answer choices:

    • A: \(-2x + 6y = -12\)

      • Rearranging gives: \(6y = 2x - 12 \Rightarrow y = \frac{1}{3}x - 2\) (slope \(= \frac{1}{3}\), parallel).
    • B: \(3x - 9y = 9\)

      • Rearranging gives: \(-9y = -3x + 9 \Rightarrow y = \frac{1}{3}x - 1\) (slope \(= \frac{1}{3}\), parallel).
    • C: \(x - 3y = 6\)

      • Rearranging gives: \(-3y = -x + 6 \Rightarrow y = \frac{1}{3}x + 2\) (slope \(=\frac{1}{3}\), parallel).
    • D: \(9x - 3y = 6\)

      • Rearranging gives: \(-3y = -9x + 6 \Rightarrow y = 3x + 2\) (slope \(= 3\), not parallel).
  3. Conclusion: Since options A, B, and C all have the same slope of \( \frac{1}{3} \) as the original line (implying they are parallel and will never intersect), they will not create a system with exactly one solution.

Only option D has a different slope, which is \(3\). Since it is not parallel to the original line, it will intersect the line at exactly one point, creating a system with exactly one solution.

Therefore, the correct answer is: D. \(9x - 3y = 6\).