Given, the equation that represents the height of an object:
![y(t)=100t-16t^2](https://img.qammunity.org/2023/formulas/mathematics/high-school/e2r2934u6rzh2yrx09r96qj7jl1r9o6a1w.png)
First, we will find the velocity of the object which is the first derivative of the height using the method of the limits
![(dy)/(dt)=\lim_(h\to a)(y(3+h)-y(3))/((3+h)-(3))](https://img.qammunity.org/2023/formulas/mathematics/high-school/edvb360p9zlfyojstmjy08pqx85z9d1wr3.png)
We will find the value of the function y(t) when t = 3, and when t = 3+h
![\begin{gathered} y(3+h)=100(3+h)-16(3+h)^2 \\ y(3+h)=300+300h-16(9+6h+h^2) \\ y(3+h)=300+300h-144-96h-16h^2 \\ y(3+h)=156+4h-16h^2 \\ y(3)=100(3)-16(3)^2=156 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/fr9sl472ixfwzk810niv8xr5fs6kq02g9d.png)
Substitute y(3+h) and y(3) into the expression of the limit
![\begin{gathered} (dy)/(dt)|_(t=3)=\lim_(h\to a)(156+4h-16h^2-156)/(3+h-3)=\lim_(h\to a)(4h-16h^2)/(h) \\ \\ (dy)/(dt)|_(t=3)=\lim_(h\to a)(4-16h) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/gei3pgrtvrblumcfapgxz1nxlkt0h9iygw.png)
Where a = 0
d) compute the instantaneous velocity at t = 3
![(dy)/(dt)|_(t=3)=100-16*2*3=4](https://img.qammunity.org/2023/formulas/mathematics/high-school/2e0ytpg2hyt3tpicoxkaodks19ffkzp83a.png)
So, the answer will be:
![\begin{gathered} (dy)/(dt)|_(t=3)=\lim_(h\to a)(4-16h) \\ a=0 \\ \\ (dy)/(dt)|_(t=3)=4\text{ ft/sec} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/v6kjj9mm9emmsmpo3axed9bgaiitlgxh0i.png)