For what values of k does the function y = cos(kt) satisfy the differential equation 9y''=16y? (Enter your answers as a comma-separated list.)k = (b) For those values of k, verify that every member of the family of functions y = A sin(kt)+ B cos(kt) is also a solution.y = A sin(kt)+ B cos(kt) y'= Ak cos(kt) Bk sin(kt) y''=Ak2 sin(kt) Bk2 cos(kt).The given differential equation9y''=16y is equivalent to9y''+16y = . Thus,LHS =9y''+16y=9(Ak2 sin(kt) Bk2 cos(kt))+16=9Ak2 sin(kt)9Bk2 cos(kt)+sin(kt)+16B cos(kt)=(169k2)A sin(kt)+cos(kt)= since k2= .