The coordinates for a point and its image are Q (-3,-5) and Q' (5, -3). Based on the mapping rules for rotations, which transformation occurred?

A. a 270-degree (counterclockwise) rotation
B. a reflection across the x-axis
C. a 90-degree (counterclockwise) rotation
D. a 180-degree rotation

1 answer

To determine which transformation occurred to map point \( Q(-3, -5) \) to point \( Q'(5, -3) \), we can analyze the coordinates and the nature of the transformations.

  1. Check each transformation option:

    • A. A 270-degree (counterclockwise) rotation:

      • A 270-degree counterclockwise rotation changes the coordinates \( (x, y) \) to \( (y, -x) \).
      • Applying this to \( Q(-3, -5) \): \[ (-5, 3) \quad \text{(not equal to } Q' (5, -3) \text{)} \]
    • B. A reflection across the x-axis:

      • Reflecting across the x-axis changes the coordinates \( (x, y) \) to \( (x, -y) \).
      • Applying this to \( Q(-3, -5) \): \[ (-3, 5) \quad \text{(not equal to } Q' (5, -3) \text{)} \]
    • C. A 90-degree (counterclockwise) rotation:

      • A 90-degree counterclockwise rotation changes the coordinates \( (x, y) \) to \( (-y, x) \).
      • Applying this to \( Q(-3, -5) \): \[ (5, -3) \quad \text{(which matches } Q' (5, -3) \text{)} \]
    • D. A 180-degree rotation:

      • A 180-degree rotation changes the coordinates \( (x, y) \) to \( (-x, -y) \).
      • Applying this to \( Q(-3, -5) \): \[ (3, 5) \quad \text{(not equal to } Q' (5, -3) \text{)} \]

After checking each option, the only transformation that correctly maps \( Q(-3, -5) \) to \( Q'(5, -3) \) is C. a 90-degree (counterclockwise) rotation.