A line segment has endpoints at (–1, 4) and (4, 1). Which reflection will produce an image with endpoints at (–4, 1) and (–1, –4)?

a reflection of the line segment across the x-axis
a reflection of the line segment across the y-axis
a reflection of the line segment across the line y = x
a reflection of the line segment across the line y = –x

1 answer

To determine which reflection produces the desired image for the endpoints of the line segment, we start by examining the endpoints of the original line segment and the desired image:

  • Original endpoints: \((-1, 4)\) and \((4, 1)\)
  • Desired endpoints: \((-4, 1)\) and \((-1, -4)\)

Now, let's explore each reflection option:

  1. Reflection across the x-axis:

    • \( (x, y) \) becomes \( (x, -y) \)
    • Reflecting \((-1, 4)\) gives \((-1, -4)\)
    • Reflecting \((4, 1)\) gives \((4, -1)\)
    • Resulting points: \((-1, -4)\) and \( (4, -1)\) (not what we need)
  2. Reflection across the y-axis:

    • \( (x, y) \) becomes \( (-x, y) \)
    • Reflecting \((-1, 4)\) gives \((1, 4)\)
    • Reflecting \((4, 1)\) gives \((-4, 1)\)
    • Resulting points: \((1, 4)\) and \((-4, 1)\) (not what we need)
  3. Reflection across the line \(y = x\):

    • \( (x, y) \) becomes \( (y, x) \)
    • Reflecting \((-1, 4)\) gives \((4, -1)\)
    • Reflecting \((4, 1)\) gives \((1, 4)\)
    • Resulting points: \((4, -1)\) and \((1, 4)\) (not what we need)
  4. Reflection across the line \(y = -x\):

    • \( (x, y) \) becomes \((-y, -x)\)
    • Reflecting \((-1, 4)\) gives \((-4, 1)\)
    • Reflecting \((4, 1)\) gives \((-1, -4)\)
    • Resulting points: \((-4, 1)\) and \((-1, -4)\) (which matches our desired endpoints)

Based on this analysis, the correct reflection is a reflection of the line segment across the line \(y = -x\).