when you reflect a point across the x-axis, the x-coordinate remains the same, but the y-coordinate is transformed into its opposite. when you reflect a point across the y-axis, the y-coordinate remains the same, but the x-coordinate is transformed into its opposite.
good to know! when you reflect a point, line, or curve across a line, think of the line as serving as a mirror. where would the reflection of each point be in the mirror?