Negin's first step to prove that the point B(7,4) lies on circle A would be to:
Negin should use the distance formula to calculate the length of segment AB.
By using the distance formula, Negin can determine the distance between the center of the circle (A(4,4)) and the point B(7,4). If this distance is equal to the radius of the circle (3), then point B lies on the circle.