Reflecting a line across an axis in a graph.

Question

The line y=3 is reflected across the x axis. What would be the equation of this new line - how would you find that? Or what if you were to reflect x=3 across the y axis, how would you solve this?

Answer 1

The line of y = 3 is a horizontal line 3 units above the x axis (draw a diagram!)

Its reflection across the x-axis is a horizontal line 3 units below.

Its equation is y = -3

The line of x = 3 is a vertical line 3 units to the right of the y-axis (draw a diagram!)

Its reflection across the y-axis is a vertical line 3 units to the left.

Its equation is x = -3