posted by Antonio .
A stone is thrown vertically upward. On its way up it passes point A with speed v, and point B,
7.85 m higher than A, with speed v. Calculate (a) the speed v and (b) the maximum height
reached by the stone above point B.
You must have copied the problem incorrectly. It cannot have the same speed "v" at two different heights.
That would violate the law of conservation of energy.