Electric potential varies with distance such that V(x) =ax-bx3; where a and b are constants. Where will the electric field intensity be zero?

• A. x=\(\frac {a}{b}\)
• B. x=\(\frac {a}{3b}\)
• C. x=\(\sqrt{\frac {a}{b}}\)
• D. x=+\(\sqrt{\frac {a}{3b}}\) and x=-\(\sqrt{\frac {a}{3b}}\)