I have 3 point charges, each with a 3D vector notation.
A is at (0, 2a, 0)
B is at (3a/2, 0, 0)
C is at (-3a/2, 0,0)
I'm usng Coulombs Law (not gone into here) & the working I have been given is;
F = (1/ 4*pi*E0) * (q2 / [rA - rB])3 (rA - rB)
F = (1/ 4*pi*E0) * (q2 / [(-3a/2, 2a, 0)]3) * (-3a/2, 2a, 0)
Which is OK for me, standard, really. It's the next bit which I don't get how to get to, with the a moving from everywhere to one place.
F = (q2 / 4*pi*E0*a2) * (-3/2, 2, 0)/(9/4 + 4)3/2
Could someone please just go through it. I'm sure I'm missing something elementary.
I included a pic of the question if that makes it easier to see.