(a) When we reflect (7,9) across the x-axis, we would get (7,-9)
(b) When we reflect (7,9) across the y-axis, we would get (-7,9)
I got my answer by understanding the reflection graph rule:
When you reflect a point across the x-axis, the x-axis will stay the same; however for the y-axis, we have to change the sign to its opposite. The term “reflect x-axis” means that we go across the x-axis. Therefore the x-axis stays the same, while the y-axis sign changes.
When you reflect a point across the y-axis, the y-axis will stay the same; however for the x-axis, we have to change the sign to its opposite. The term “reflect y-axis” means that we go across the y-axis. Hence why the y-axis stays the same, while the x-axis sign changes.