If Three charges are on the $y$-axis. Charges $-q$ are at $y= \pm d$ and charge $+2 q$ is at $y=0$.
a. Determine the electric field $\vec{E}$ along the x-axis.
b. Verify that your answer to part a has the expected behavior as $x$ becomes very small and very large.
c. Sketch a graph of $E_x$ versus $x$ for $0 \leq x \leq \infty$.