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"...