خیلی ممنون.خودم تونستم بنویسمش
اینه:
program newton
implicit none
real::a,b,x1,x2,k,p,r,s
print*," lotfan hodood baze ra vared konid"
1 read*,a,b
k=(a**3)-(3*a)+1
p=(b**3)-(3*b)+1
if((k*p)<0) then
x1=(a+b)/2
else
print*,"dar in baze rishee vojod nadarad.dobare say konid"
go to 1
end if
2 r=(x1**3)-(3*x1)+1
s=(3*x1**2)-3
x2=x1-(r/s)
if(abs(x2-x1)<0.001) then
print*,x1
print*,x2
else
x1=x2
go to 2
end if
end