Theorem: IMOSL.IMO2012A5.Case3.CommCase.pow_four_Eq2 (IMOSLLean4/IMO2012/A5/A5Cases/Case3.lean)

State before:
R : Type u_2
S : Type u_1
inst✝³ : CommSemiring R
inst✝² : CharTwo R
inst✝¹ : CommRing S
inst✝ : NoZeroDivisors S
f : R → S
hf : NontrivialGood f
x : R
⊢ f ((x ^ 2) ^ 2 + 1) = (f (x + 1) ^ 2 - 1) ^ 2 - 1
Tactic:
rw [← pow_four_Eq1 hf, add_one_sq, add_one_sq]
State after:
no goals