I have just solved a problem about electric potential and it is: " A positive point charge of 1.0 nC is located at position x=0.00 . A second point charge q=-1.0 nC is located at x=0.10 m. (a) What is the value of the electric potential on the x-axis at x=0.3 m ? (b) What is the value of the electric potential on the at x=-0.050 m ? " I have solved (a) and its answer is "-15". And I know that electric potential is a scalar quantity. Explain that.