where $\bar{\nabla}=\hat{i} \frac{\partial}{\partial x}+\hat{j} \frac{\partial}{\partial y}+\hat{k} \frac{\partial}{\partial z}$
$\therefore \quad \vec{E}=-\left[\hat{i} \frac{\partial V}{\partial x}+\hat{j} \frac{\partial V}{\partial y}+\hat{k} \frac{\partial V}{\partial z}\right]$
Here, $V=4 x^{2} \quad \therefore \quad \vec{E}=-8 x \hat{i}$
The electric field at point $(1,0,2)$ is
$\vec{E}_{(1,0,2)}=-8 \hat{i}\,Vm^{-1}$
So electric field is along the negative $X$ -axis.



Assume that the electrostatic potential is zero at an infinite distance from the spherical shell. The electrostatic potential at a distance $R$ $(a < R < b)$ from the centre of the shell is (where $K = $ $\frac{1}{{4\pi {\varepsilon _0}}}$)