Coulomb's Law, net electrostatic force

[nn3568]

Homework Statement

A particle with charge −9 μC is located on the x-axis at the point 8 cm, and a second particle with charge 5 μC is placed on the x-axis at 6 cm. The Coulomb constant is 8.9875 × 109 N · m2/C2. What is the magnitude of the total electrostatic force on a third particle with charge 2 μC placed on the x-axis at −2 cm? Answer in units of N.

Homework Equations

Coulomb's Law
f_e = (kq₁q₂)/(d²)

The Attempt at a Solution

(8.9875e9 * 2e-6 * 5e-6) / (0.08^2) = 14.04296875
(8.9875e9 * 5e-6 * -9e-6) / (0.02^2) = -983.0078125
14.04296875 + -983.0078125 = -997.0507813
magnitude 997.0507813

Why is this wrong? What can I do to make it right?

 

[Doc Al]

(8.9875e9 * 5e-6 * -9e-6) / (0.02^2) = -983.0078125

You want the force on the 2μC charge.

 

[nn3568]

Thank you so much!