Question

Triangle ABC underwent a sequence of transformations to give triangle A′B′C′. Which transformations could not have taken place? A. a reflection across the line y = x followed by a reflection across the line y = -x B. a reflection across the x-axis followed by a reflection across the y-axis C. a rotation 180° clockwise about the origin followed by a reflection across the line y = x D. a reflection across the y-axis followed by a reflection across the x-axis

Answer 1

C. a rotation 180° clockwise about the origin followed by a reflection across the line y = x

Explanation:

Let us assume that the coordinate of A in triangle ABC is A(x, y)

A) If there is a reflection across line y = x, the new coordinate is at A'(y, x).

If a reflection across the line y = -x is then followed, the new coordinate is at A"(-x, -y)

B) If there is a reflection across line x axis, the new coordinate is at A'(x, -y).

If a reflection across the line y axis is then done, the new coordinate is at

A"(-x, -y)

C) If there is a rotation 180° clockwise about the origin, the new coordinate is at A'(-x, -y).

If a reflection across the line y = x is then followed, the new coordinate is at A"(-y, -x)

D) B) If there is a reflection across line y axis, the new coordinate is at A'(-x, y).

If a reflection across the line x axis is then done, the new coordinate is at

A"(-x, -y)

Since only option C has a different result from the remaining options, hence option C would not five triangle A'B'C'

Answer 2

C. a rotation 180° clockwise about the origin followed by a reflection across the line y = x

Explanation:

Let us assume that the coordinate of A in triangle ABC is A(x, y)

A) If there is a reflection across line y = x, the new coordinate is at A'(y, x).

If a reflection across the line y = -x is then followed, the new coordinate is at A"(-x, -y)

B) If there is a reflection across line x axis, the new coordinate is at A'(x, -y).

If a reflection across the line y axis is then done, the new coordinate is at

A"(-x, -y)

C) If there is a rotation 180° clockwise about the origin, the new coordinate is at A'(-x, -y).

If a reflection across the line y = x is then followed, the new coordinate is at A"(-y, -x)

D) B) If there is a reflection across line y axis, the new coordinate is at A'(-x, y).

If a reflection across the line x axis is then done, the new coordinate is at

A"(-x, -y)

Since only option C has a different result from the remaining options, hence option C would not five triangle A'B'C'