At what coordinate on the x axis is the electric field produced by the particles equal to zero?

Question

Two particles are fixed to an x axis: particle 1 of charge q₁ = 2.18 × 10^-8 C at x = 17.0 cm and particle 2 of charge q₂ = -4.41q₁ at x = 78.0 cm. At what coordinate on the x axis is the electric field produced by the particles equal to zero? Tolerance is +-1 in the 3rd significant digit.

Answer 1

The location will be to the left of 17cm and can be found by solving -kQ1/r + 4.41kQ1/(78-r) = 0 yielding r= 14.42 cm