The equation should be
x 1 ( t ) = e λ t = e − ω n t , x 2 ( t ) = t e λ t = t e − ω n t {\displaystyle x_{1}(t)=e^{\lambda t}=e^{-\omega _{n}t},\qquad x_{2}(t)=te^{\lambda t}=te^{-\omega _{n}t}}
Return to errata.