Answer
See below.
Work Step by Step
For any body moving between two points x and $x_{0}$, the average velocity is given as:
$v=\frac{x(t_{1})-x(t_{0})}{t_{1}-t_{0}}$
When the limit is applied at a particular point, it becomes the instantaneous velocity of the body:
$v(t_{0})=\lim\limits_{t \to t_{0}}\frac{x(t_{1})-x(t_{0})}{t_{1}-t_{0}}$
Similarly, the acceleration is given as the rate of change of the velocity:
$a(t_{0})=\lim\limits_{t \to t_{0}}\frac{v(t_{1})-v(t_{0})}{t_{1}-t_{0}}$
