subroutine Start_Values()
use work

implicit real(8) (a-h, o-z)
! computes x(-1), x(-2), x(-3), x(-4), ...
! Via BDF of order 1, 2, 3, 4


xa(0,:) =x0(:)

! solutia exacta:
! x  =(100/99)*exp(-t) -(1/99)*exp(-100*t)
! x' =-(100/99)*exp(-t) +(100/99)*exp(-100*t)


do l=-1, -k+1, -1
t =t0 +l*h

xa(l,1) =( 100_8*dexp(-t) -dexp(-100_8*t) )/99_8
xa(l,2) =( -100_8*dexp(-t) +100_8*dexp(-100*t) )/99_8
enddo

END subroutine Start_Values
