f(t) = - 16(t - 1)² + 24
the equation of a parabola in vertex form is
y = a(x - h)² + k
where (h, k) are the coordinates of the vertex and a is a multiplier
here the vertex = (1, 24)
y = a(t - 1)² + 24
to find a substitute the starting point (0, 8) into the equation
8 = a + 24 ⇒ a = 8 - 24 = - 16
f(t) = - 16(t - 1 )² + 24