Physics
posted by Lauren .
A +3.0 nC charge is at x=0 cm and a 1.0 nC charge is at x=4 cm. At what point or points on the xaxis is the electric potential zero?

Wherever 3/x  1/4x = 0 , the electric potential is zero.
x is the distance from the +3 nC charge and 4x is the distance from the 1 nC charge.
To omit the absolute value   signs and solve algebraically, you need to write and solve separate equations for x<0, 0<x<4 and x>4
For 0<x<4,
3/x  1/(4x) = 0
3/x = 1/(4x)
12  3x = x
x = 3
See if there are solutions in the other regions.