Which composition transformation occurs in the following? (x,y) -> (y + 5, -x)

a. a reflection across the x-axis and a translation to the left by -5
b. A 90-degree clockwise rotation and translation to the right by 5
c. a reflection across the y-axis and a translation to the right by 5
d. A 180-degree rotation and a translation to the right by 5

1 answer

To analyze the transformation given by the function \((x,y) \to (y + 5, -x)\), let's break it down step by step.

  1. Identify the transformations:
    • The first part of the transformation takes \(x\) to \(-x\). This reflects the point across the y-axis.
    • The second part of the transformation takes \(y\) to \(y + 5\). This translates the point upward by 5 units.

However, because of the ordering of the transformations, we can express the transformation in terms of effects on the coordinates.

Transformations:

  • Start with the point \((x, y)\).
  • First, reflect across the y-axis: \((x, y)\) becomes \((-x, y)\).
  • Then, translate upwards: \((-x, y)\) becomes \((-x, y + 5)\).

This means we need to translate the second coordinate, rather than the first coordinate, which changes the vertical position rather than the horizontal position.

So, our complete transformation can be simplified to: \[ (-x, y + 5) \]

  1. Match to the options:
    • The first option indicates a reflection across the x-axis and a translation left, which is not correct for our transformation.
    • The second option mentions a 90-degree clockwise rotation, which doesn't match our transformation either.
    • The third option mentions a reflection across the y-axis and a translation to the right, which also doesn't capture the upward translation.
    • The last option (d) suggests a 180-degree rotation (which gives \((-x, -y)\)) and translation, which does not apply either.

Based on the reflection and translation aspects, option d is misleading as it does not precisely describe the transformation.

Thus, the transformation is a reflection across the y-axis and a translation upward by 5, which closely matches the information, but none of the options reflect that correctly.

The correct description should state: reflection across the y-axis and an upward translation by 5. Since this phrasing is not an available option, ensure to select the nearest possible description based on context or consider clarifying the necessary transformations.