Let A = (4,-1)$, B = (6,2) and C = (-1,2). There exists a point X and a constant k such that for any point P$, PA^2 + PB^2 + PC^2 = 3PX^2 + k. Find the constant k.
I don't know what to do. I tried solving by plugging in the coordinates but it didn't help. Could someone please help? Thank you!
