Theorem: IMOSL.IMO2012A5.Case3.Eq2_v2 (IMOSLLean4/IMO2012/A5/A5Cases/Case3.lean)

State before:
R : Type u_2
S : Type u_1
inst✝³ : Semiring R
inst✝² : CharTwo R
inst✝¹ : Ring S
inst✝ : NoZeroDivisors S
f : R → S
hf : NontrivialGood f
x : R
⊢ f (x * x) = f (x + 1) ^ 2 - 1
Tactic:
rw [← Eq2 hf, add_one_mul_self, add_add_cancel_right]
State after:
no goals