H=3+14t-5t^2
What is its maximum height

12.8

Step-by-step explanation:

Given a parabola in standard form , ax² + bx + c : a ≠ 0

Then the x- coordinate of the vertex is

= -

h = 3 + 14t - 5t² ← is in standard form

with a = - 5 and b = 14, thus

= - = 1.4

Substitute t = 1.4 into h for maximum height

h = 3 + 14(1.4) - 5(1.4)²

   = 3 + 19.6 - 9.8 = 12.8