Marisol calculated the slope incorrectly in Step 2. The correct formula for the slope (m) between two points \((x_1, y_1)\) and \((x_2, y_2)\) is given by:
\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]
In the provided steps, Marisol labeled the points as \((x_1, y_1) = (-1, 4)\) and \((x_2, y_2) = (3, 10)\). Therefore, \((x_1, y_1)\) yields \(y_1 = 4\) and \(x_1 = -1\) while \((x_2, y_2)\) gives \(y_2 = 10\) and \(x_2 = 3\).
However, in her calculation, she used:
\[ \frac{10 - 3}{4 - (-1)} = \frac{7}{5} \]
This suggests that she took \(y_2 - y_1\) correctly as \(10 - 4 = 6\) and added to it \(y_1 - x_1\) incorrectly on the bottom rather than calculating \(x_2 - x_1\) as \(3 - (-1) = 4\).
Marisol actually computed:
\[ \frac{y_2 - y_1}{y_1 - x_1} \]
instead of the correct slope calculation.
The correct implication is:
Marisol computed \(\frac{y_2 - y_1}{x_2 - x_1}\) correctly for \(y\) values but incorrectly handled the \(x\) values. This fits with the statement that says:
"Marisol computed \(\frac{y_2 - x_2}{y_1 - x_1}\)."
Thus, the best option explaining her error is:
Marisol computed \(\frac{y_2 - x_2}{y_1 - x_1}\).