1. The problem statement, all variables and given/known data I have 3 masses in 1-D connected by two springs. A driving force is exerted on the first mass and i need to derive the equation of motion of the last mass. I have worked out the Lagrangian to determine the equations of motion but cannot solve for z. 2. Relevant equations The equations are d^2(x)/dt^2 = A(y + B*cos(omega*t) - x) d^2(y)/dt^2 = A(z+x-2y) d^2(x)/dt^2 = A(y-z) x,y,and z are the positions of the masses in 1-D and A,B are constants 3. The attempt at a solution I tried general solutions of x= Csin(kt) +Dcos(kt) ect and also x= Ce^(ikt) but could not work it through. Where am i supposed to start?