Question is: Two point charges, +1 C on the left and -4 C on the right, are separated by 1 meter. At what point on the line joining the two charges is the electric field zero?

We don't like to just give away answers here.

Think about how the field is related to the distance, then have a go at finding the equilibrium point. Does the equilibrium point even exist for the charges you have?

Have a go at the answer, I'll be back in 40 minutes to have a look at your answer and help you if you are having trouble, if nobody else has jumped in.