A positive point charge q is placed at x = a, and a negative point charge -q

Question:

A positive point charge q is placed at x = a, and a negative point charge -q is placed at x = -a.
(a) Find the magnitude and direction of the electric field at x = 0.
(b) Derive an expression for the electric field at points on the x axis. Use your result to graph the x-component of the electric field as a function of x, for values of x between -4a and +4a.