Multiple Choice Question

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 = -2

B. 3x - 9y = 9

C. x - 3y = 6

D. 9x - 3y = 6

1 answer

To find an equation that results in a system of equations with exactly one solution, we need to identify a line that has a different slope than the line represented by the points provided. The points you mentioned create a linear pattern, and we can determine the slope of that line.

Let's find the slope using two points from the list, for example, (0, -2) and (3, -1):

  1. Calculate the change in y (Δy) and change in x (Δx):

    • Δy = -1 - (-2) = 1
    • Δx = 3 - 0 = 3
  2. The slope (m) is calculated as:

    • m = Δy / Δx = 1 / 3

Thus, the slope of the line represented by the points is \( \frac{1}{3} \).

For a system of equations to have exactly one solution, the new line must have a different slope than \( \frac{1}{3} \).

Now let's check the slope of each of the given equations to see which one has a different slope:

A. -2x + 6y = -2
Rearranging gives:
\[ 6y = 2x - 2 \quad \Rightarrow \quad y = \frac{1}{3}x - \frac{1}{3} \]
(Slope is \( \frac{1}{3} \))

B. 3x - 9y = 9
Rearranging gives:
\[ -9y = -3x + 9 \quad \Rightarrow \quad y = \frac{1}{3}x + 1 \]
(Slope is \( \frac{1}{3} \))

C. x - 3y = 6
Rearranging gives:
\[ -3y = -x + 6 \quad \Rightarrow \quad y = \frac{1}{3}x - 2 \]
(Slope is \( \frac{1}{3} \))

D. 9x - 3y = 6
Rearranging gives:
\[ -3y = -9x + 6 \quad \Rightarrow \quad y = 3x - 2 \]
(Slope is \( 3 \))

From the analysis, we see that option D has a slope of 3, which is different from \( \frac{1}{3} \). Thus, it will intersect with the original line at exactly one point.

Therefore, the answer is:

D. 9x - 3y = 6