Question

Use matrices to determine the vertices of the reflected figure. Then graph the image and the pre-image on the same coordinate grid.

Triangle XYZ with vertices X(2, -9), Y(-6, 0) and Z(-5, -5), reflected over the y-axis.
A.
B.
C.
D.
(pictures below)

Answer 1

The correct answer is graph C, or the third option.

Just got it right on edge 2020, hope this helps!! :)

Answer 2

• see below for the matrix multiplication
• graph C

Explanation:

Reflection across the y-axis is a left-right reflection that changes only the sign of the x-coordinate. The transformation matrix (as for any rotation and/or reflection) can be 2-dimensional, and can left-multiply the coordinate matrix that has coordinate pairs as column vectors. The transformed coordinates show up as column vectors in the result matrix.

The only graphs showing left-right reflections are those of choices C and D. Only choice C has the points properly plotted on the graph.