Question

Triangle DEF has vertices at D(−3, 5), E(−10, 4), and F(−1, 8). Triangle D′E′F′ is the image of triangle DEF after a reflection. Determine the line of reflection if D′ is located at (−3, −5). y = −5 x = −3 y-axis x-axis

Answer 1

We know that a reflection about the x-axis is given by:

$(x,y)\rightarrow(x,-y)$

We notice that the point D(-3,5) is taken to the point D'(-3,-5) which means that we changed the sign of the y-coordinate which is exactly what the reflection aboth the x-axis does.

Therefore, the line of reflection is the x-axis