Algoritmo - Raiz complexas

PROGRAM newton2
IMPLICIT NONE
REAL(8):: precisao, x, y
INTEGER(2):: n
PRINT*, "digite valor inicial para x"
READ*, x
n=0
precisao=1D0

DO WHILE (precisao>0.00001D0)
y = (4*x**3-20*x)*EXP(-x)-(x**4-10*x**2)*EXP(-x)
precisao = ABS(x-y)
x=y
PRINT*, n, x
n=n+1
ENDDO
PRINT* , "A RAIZ DA FUNCAO E",y
PRINT* , "com", n, "interacoes"

END PROGRAM newton2