Select the lines from this list that are perpendicular: y - 2 = 3/4 (x + 1), y = - 3/4 x + 12, 4x - 3y = -6, 5x - 3y = - 3

1 answer

To determine which lines are perpendicular from the given equations, we need to find the slopes of each line. Two lines are perpendicular if the product of their slopes is -1.

  1. Line 1: \( y - 2 = \frac{3}{4}(x + 1) \)

    Rearranging this into slope-intercept form (y = mx + b): \[ y - 2 = \frac{3}{4}x + \frac{3}{4} \] \[ y = \frac{3}{4}x + \frac{3}{4} + 2 \] \[ y = \frac{3}{4}x + \frac{11}{4} \] The slope is \( m_1 = \frac{3}{4} \).

  2. Line 2: \( y = -\frac{3}{4}x + 12 \)

    The slope is \( m_2 = -\frac{3}{4} \).

  3. Line 3: \( 4x - 3y = -6 \)

    Rearranging into slope-intercept form: \[ -3y = -4x - 6 \] \[ y = \frac{4}{3}x + 2 \] The slope is \( m_3 = \frac{4}{3} \).

  4. Line 4: \( 5x - 3y = -3 \)

    Rearranging into slope-intercept form: \[ -3y = -5x - 3 \] \[ y = \frac{5}{3}x + 1 \] The slope is \( m_4 = \frac{5}{3} \).

Now let's check for perpendicularity:

  • Line 1: \( m_1 = \frac{3}{4} \)

  • Line 2: \( m_2 = -\frac{3}{4} \)

    • Product: \( \frac{3}{4} \cdot -\frac{3}{4} = -\frac{9}{16} \) (NOT perpendicular)
  • Line 1: \( m_1 = \frac{3}{4} \)

  • Line 3: \( m_3 = \frac{4}{3} \)

    • Product: \( \frac{3}{4} \cdot \frac{4}{3} = 1 \) (NOT perpendicular)
  • Line 1: \( m_1 = \frac{3}{4} \)

  • Line 4: \( m_4 = \frac{5}{3} \)

    • Product: \( \frac{3}{4} \cdot \frac{5}{3} = \frac{15}{12} \) (NOT perpendicular)
  • Line 2: \( m_2 = -\frac{3}{4} \)

  • Line 3: \( m_3 = \frac{4}{3} \)

    • Product: \( -\frac{3}{4} \cdot \frac{4}{3} = -1 \) (PERPENDICULAR)
  • Line 2: \( m_2 = -\frac{3}{4} \)

  • Line 4: \( m_4 = \frac{5}{3} \)

    • Product: \( -\frac{3}{4} \cdot \frac{5}{3} = -\frac{15}{12} \) (NOT perpendicular)
  • Line 3: \( m_3 = \frac{4}{3} \)

  • Line 4: \( m_4 = \frac{5}{3} \)

    • Product: \( \frac{4}{3} \cdot \frac{5}{3} = \frac{20}{9} \) (NOT perpendicular)

Conclusion: The only pair of lines that are perpendicular is:

  • Line 2: \( y = -\frac{3}{4}x + 12 \)
  • Line 3: \( 4x - 3y = -6 \)

Thus, the lines that are perpendicular are:

  • y = -3/4 x + 12
  • 4x - 3y = -6