Negin's first step to prove that point B(7,4) lies on circle A should be to use the distance formula to calculate the length of segment AB.
The distance formula will help determine if the distance between the center of the circle (4, 4) and point B (7, 4) is equal to the radius of the circle (3). If the distance is 3, then point B lies on the circle.
So, the correct response is: Negin should use the distance formula to calculate the length of segment AB.