Fortran Newton Raphson Method on Fortran90

[jhosamelly]

Here's what I need to do:

"Compare the effectiveness of the bisection method and Newton’s method for the
equation x^3−2x−2 = 0 which has a single root between x=−4 and x = 2."So far I've done

ok. this is working but of course I need to do iteration which I don't know how. Can someone teach me please? I'm trying the Newton-Raphson Method first.

Thanks for the help in advance.EDITED: Sorry, I posted the wrong pic earlier. Here's the correct one.

 

[gsal]

program nr
real:: x, xnew, err

write(*,*) "starting x?:"
read(*,*) x

do
    xnew = x - ( (x**3 - (2*x) - 2) / ( ( 3*(x**2) )-2) )
    err = 100*abs( (xnew-x)/x )
    x = xnew
    write(*,*) "x = ", xnew, "  error = ", err
    if (err < 0.000001) exit
end do

end program nr

 

[jhosamelly]

thanks ) Is that the iteration already?

 

[gsal]

Yes.

Isn't it? Run it and verify the solution