Question

Select ALL of the following that would reflect the following triangle onto itself.

Answer 1

Over x = 4

Explanation:

In its current configuration, our triangle only has vertical symmetry - we can only flip it onto itself if it's over a verticle line. This immediately eliminates our two horizontal lines from the equation: y = 4 and the x axis.

That leaves us chosing between the y axis or the line x = 4. Now that we know the type of symmetry this triangle has (vertical), we need to figure out where to put the line of symmetry. The y axis won't do, since a reflection over that will move the triangle to the far left of the page. So it must be the line x = 4.