Are the pairs of lines parallel, perpendicular, or intersecting? (3 points)

2x - y = 7

3x - 4y = - 8

y - 6 = 1/4 * (x + 2)

y = - 4x - 10

y = - 2/3 * x + 7

- 2x - 3y = 12

# Intersecting

>

#Perpendicular

# Parallel

1 answer

To determine the relationship between the pairs of lines given by their equations, we can convert all of the equations to slope-intercept form (y = mx + b), where m represents the slope. Two lines are parallel if they have the same slope, perpendicular if the product of their slopes is -1, and intersecting if neither condition applies.

Let's find the slopes for each pair of lines.

  1. Different pairs of lines:

    • First Pair:

      1. \( 2x - y = 7 \) \[ y = 2x - 7 \quad \text{(slope } m_1 = 2\text{)} \]

      2. \( 3x - 4y = -8 \) \[ 4y = 3x + 8 \implies y = \frac{3}{4}x + 2 \quad \text{(slope } m_2 = \frac{3}{4}\text{)} \]

    • Since \( m_1 \neq m_2 \) and \( m_1 \cdot m_2 \neq -1 \), these lines are intersecting.

    • Second Pair:

      1. \( y - 6 = \frac{1}{4}(x + 2) \) \[ y - 6 = \frac{1}{4}x + \frac{1}{2} \implies y = \frac{1}{4}x + 6.5 \quad \text{(slope } m_3 = \frac{1}{4}\text{)} \]

      2. \( y = -4x - 10 \) \[ (slope } m_4 = -4\text{)} \]

    • Since \( m_3 \cdot m_4 = \frac{1}{4} \cdot -4 = -1 \), these lines are perpendicular.

    • Third Pair:

      1. \( y = -\frac{2}{3}x + 7 \) \[ (slope } m_5 = -\frac{2}{3}\text{)} \]

      2. \( -2x - 3y = 12 \) \[ 3y = -2x - 12 \implies y = -\frac{2}{3}x - 4 \quad \text{(slope } m_6 = -\frac{2}{3}\text{)} \]

    • Since \( m_5 = m_6 \), these lines are parallel.

In summary:

  1. The first pair is intersecting.
  2. The second pair is perpendicular.
  3. The third pair is parallel.