Quad Int norm add le twice

import Mathlib.Algebra.QuadraticAlgebra.Basic
import Mathlib.Algebra.Ring.Basic
import Mathlib.Algebra.Ring.Equiv
import Mathlib.Data.Finset.Card
import Mathlib.Data.Finset.Prod
import Mathlib.Data.Int.Interval
import Mathlib.Data.Int.Sqrt
import Mathlib.Tactic.Linarith
import Mathlib.Tactic.LinearCombination
import Definitions.Def_D1Bound5_Coordinates_Definitions

section
namespace D1Bound5
open QuadInt




theorem _root_.D1Bound5.quadInt_norm_add_le_twice {tau nu : ℤ}
    (hd : 0 < discriminant tau nu) (x y : QuadInt tau nu) :
    (x+y).norm ≤ 2*x.norm+2*y.norm := by sorry































end D1Bound5
end