$6\mathrm{.}26.$ Consider the viscoelastically damped system of Fig. P$6\mathrm{.}26.$ The system differs from the

viscously damped system by the addition of the spring k$\_(1),$ which introduces one more

coordinate, x$\_(1).$ to the system. The equations of motion for the system in inertial coordi$-$

nates x and x$\_(1)$ are

mx$^()=-$kx$-$c$(($x$^())-$x$\_(1)^())+$F

$0=$c$(($x$^())-$x$\_(1)^())-$k$\_(1)$x$\_(1)$

Write the equation of motion in matrix form.