Final answer:
A reflection across the y-axis is a transformation that flips a figure over the y-axis. The rule for this transformation is to change the sign of the x-coordinate while keeping the y-coordinate unchanged.
Step-by-step explanation:
A reflection across the y-axis is a transformation that flips a figure over the y-axis. The rule for this transformation is to change the sign of the x-coordinate while keeping the y-coordinate unchanged.
For example, if we have a point (3, 2) and we want to reflect it across the y-axis, the new coordinates would be (-3, 2).
This rule applies to all points in a figure, resulting in a mirror image of the original figure with respect to the y-axis.