residocity of elements in an extension of $\mathbb{F}_p$

edit

Consider the following code :-

p=10010113
F=GF(p)
R=PolynomialRing(F,'x')
f=x^5 + 3212480*x^4 + 5943978*x^3 + 1041193*x^2 + 3212605*x + 4505026
F1.<a>=F.extension(f)
R1=PolynomialRing(F1,'x')
f1=derivative(f(x),x)
b=R1(f1(a))
b=F1(b)

Now since b $in $ F1 . Therefore F1(b**p^5-1) should output 1, but I am getting this output

sage: F1(b**(((p^5)-1)))
/usr/lib/sagemath/local/bin/sage-ipython:1: RuntimeWarning: invalid value encountered in power
  #!/usr/bin/env python
9745575*a^4 + 8100949*a^3 + 6855548*a^2 + 351457*a + 548263

Which is absurd !