simp only [isGood_iff, h₂, abs_of_pos (sub_pos.2 h₁), add_add_sub_cancel, and_true]
x A : ℝ
hx : 1 < x
h₁ : 1 < √(2 * x - 1)
h₂ : 1 / 2 ≤ x
⊢ IsGood x A ↔ A = √(4 * x - 2)
x A : ℝ
hx : 1 < x
h₁ : 1 < √(2 * x - 1)
h₂ : 1 / 2 ≤ x
⊢ √(2 * x - 1) + √(2 * x - 1) = A * √2 ↔ A = √(4 * x - 2)