Finding electric potential given two point charges

[Mickael14]

Homework Statement

Find the potential at points P1, P2, P3, and P4 in the diagram due to the two given charges.

Homework Equations

V_P =k∑q_i/r_i
p = q ⋅ d

The Attempt at a Solution

I'm not sure how to approach the problem. I thought about using that given equation four times and adding it all together, but I was wondering if there was an easier way? If not, I would like to know if this is correct...
V₁ = (9 x 10⁹)[(5x10^-3)/.02) - (-10x10^-3)/.06)]
Then repeat these steps for V₂, V₃, and V₄.

Then V_T would be V₁ + V₂ + V₃ + V₄.

 

[Mickael14]

Another question whenever someone sees this... Would I need to use the negative in the Q₂ charge? I know V is scalar, but I was wondering because that would significantly change my answer.

 

[kuruman]

Would I need to use the negative in the Q2 charge?

Yes.

V1 = (9 x 10⁹)[(5x10^-3)/.02) - (-10x10^-3)/.06)]

Too many negative signs.

... but I was wondering if there was an easier way?

Do it the "brute force" method first by doing the calculation 4 times. Then you will discover something about the symmetry of the situation. Hint: Electric potential due to a point charge depends on distance from the charge but not on direction.