I have the equation x=ct-4.9t^2 where x=height, t=time for a body projected vertically up from the ground.

I want to find the initial velocity if the body just reaches a height of 250m using calculus (I already found the answer with Physics-see below).

The maths

x=ct-4.9t^2

x`=c-9.8t, c=9.8t

x``=-9.8

Can someone help?

s=(final velocity^2-initial velocity^2)/2A

250= (0^2-x^2)/2(-9.8)

X=70m/s