Answer
See the detailed answer below.
Work Step by Step
$$\color{blue}{\bf [a]}$$
What is the electric potential in a region where the electric field is given by
$$E_z=2az\;\rm V/m$$
where $a$ is constant? where the electric potential at $z=0$ m is zero.
$$\color{blue}{\bf [b]}$$
Solving the given formula
$$-2az dz=dV$$
Taking the integral,
$$V=-2a\int zdz$$
$$V_z=- a z^2+\rm constant$$
at $z=0$, $V_z=\rm constant$ which is given above.
Thus,
$$\boxed{V_z=- a z^2+10}$$
