how can i solve this problem using professor's suggestion

Recall the two coupled masses undergoing linear oscillations in Example 8. p.22-25. Solve a simple extension of this problem with three indentical masses and four identical springs. Solve for the physical motion by first solving for the eigenvalues and eigenvectors as we did in lecture for two masses. We also refered to these values and vectors together as the eigen modes, I expect that we will have short discussions about the solution for the motion in each class period. displace at K mm mm MI M MI -a ->