Question

The vertices of a triangle are P(-4,1),Q(-2,-8), and R(8,-1). What are the vertices of the image reflected across the y-axis?

Answer 1

P would be (4,1), Q would be (2,-8) and R would be (-8,-1).
In this case, where you are reflecting over the Y axis, you just switch the values of X (from negative to positive and vice versa)! When reflecting over the X axis, you do the same but you switch the Y values from negative to positive (and vice versa).
Hope this helped!