Question

The triangle STU shown on the coordinate grid below is reflected once to map onto triangle S'T'U': Triangle STU drawn on a 4 quadrant coordinate grid with vertices S is at 8, 6. T is at 2, 2. U is at 5, 1. If vertex T' is at (2, −2), what are the coordinates of vertex S'?

Answer 1

Given that triangle STU is reflected once to map onto triangle S'T'U'.
Given that triangle STU has vertices S(8, 6), T(2, 2), U(5, 1).

If vertex T' is at (2, −2), this means that triangle STU is refrected across the x-axis.

A refrection across the x-axis results in an image that has the same x-value as the pre-image but a y-value that has the opposite sign of the y-value of the pre image.

Thus, a point, say (x, y), refrected over the x-axis will result in an image with coordinate (x, -y)

Therefore, given that the coordinate of S is (8, 6), then the coordinates of vertex S'  is (8, -6).