have : 1 ≤ abs a.im := by rwa [← Int.abs_lt_one_iff, not_lt] at hb
case neg
a : ℤ√(-3)
h : |a.re| ≠ 1
H : |a.re| < 1
this : a.re = 0
hb : ¬a.im = 0
⊢ 3 * a.im * a.im ≠ 1
case neg
a : ℤ√(-3)
h : |a.re| ≠ 1
H : |a.re| < 1
this✝ : a.re = 0
hb : ¬a.im = 0
this : 1 ≤ |a.im|
⊢ 3 * a.im * a.im ≠ 1