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now my differential equation is

NDSolve[{x''[t] + Rx'[t] - Sum from i=1to3 of (x-x[t])/(rootof(x-x[t])^2 +[y-y[t])^2 +d^2)^3 + Qx[t]==0,

{y''[t] + Ry'[t] - Sum from i=1to3 of (y-y[t])/(rootof(x-x[t])^2 +[y-y[t])^2 +d^2)^3 + Qy[t]==0, x[0]==-.95, y[0]==0.09, x'[0]==0, y'[0]==0}, {x,y}, {t,0,100}, MaxSteps -> 1000]

I have assigned values to R Q and d, and please note than the x's and y's which are not of t, should be subscript i.

I get the error,

"The first argument must have both an equation and an initial condition."

I keep compare my equation to other example equations but I can't see whats wrong.

Any anyone shed any light?

Very much appreciated.