Show that the resolvent operator R λ defined in Theorem 38.1 is a symmetric operator, that is, if   Show that if the resolvent operator Rλ is a symmetric operator, then the transition operators Pt are...

Show that the resolvent operator R_λ
defined in Theorem 38.1 is a symmetric operator, that is, if

Show that if the resolvent operator Rλ is a symmetric operator, then the transition operators Pt are also symmetric: if
  then