The final answer is positive as shown in the printed solution. The field is pointing in the +x direction. E field = negative derivative of the potential times unit vector. If potential at x was negative as your are suspecting, and 0 at infinity, the derivative is > 0 and negative derivative is <0 , giving a field pointing in the wrong direction. See the link posted:
lamplamp
- 1.5k
- 1
- 13
- 24