Line A passes through points (4,7) and (9,9). Line B passes through points (3,10) and (1,15). Are lines A and B parallel or perpendicular?

1 answer

To determine if lines A and B are parallel or perpendicular, we need to find the slopes of both lines.

Step 1: Find the slope of Line A

The formula for the slope (\(m\)) given two points \((x_1, y_1)\) and \((x_2, y_2)\) is:

\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]

For Line A, the points are \((4, 7)\) and \((9, 9)\):

\[ m_A = \frac{9 - 7}{9 - 4} = \frac{2}{5} \]

Step 2: Find the slope of Line B

Using the same formula for Line B, with points \((3, 10)\) and \((1, 15)\):

\[ m_B = \frac{15 - 10}{1 - 3} = \frac{5}{-2} = -\frac{5}{2} \]

Step 3: Compare the slopes

  • Lines are parallel if their slopes are equal: \(m_A = m_B\).
  • Lines are perpendicular if the product of their slopes is \(-1\): \(m_A \cdot m_B = -1\).

Now let's check the conditions:

  • Check if they are parallel: \[ \frac{2}{5} \neq -\frac{5}{2} \] So, they are not parallel.

  • Check if they are perpendicular: \[ m_A \cdot m_B = \left(\frac{2}{5}\right) \cdot \left(-\frac{5}{2}\right) = -1 \]

Since the product of the slopes is \(-1\), the lines are perpendicular.

Conclusion: Lines A and B are perpendicular.