Suppose we have typical chain of strings with masses, attached to the walls (W) at each side
W-----m-----m--------W x=0 x=6 x=12 x=21
So if we let this system oscillate for a while (assuming there is some damping), it will end up in equilibrium state, where all 3 springs have same lengths of 7.
My question is: how to solve this problem, if we assume that springs and their connection points (m) are mass-less? Is it solvable? What happens to differential equations, derived from $$ F=m \ddot x = -kx~? $$