Répondre :
on a : lxl ≤ 1/2 et lYl ≤ 1
-1/2 ≤ x ≤ 1/2 et -1 ≤ y ≤ 1
0 ≤ x² ≤ 1/4
0 ≤ 4x² ≤ 1
-1 ≤ 4x²y ≤ 1
-3/2 ≤ x+y ≤ 3/2
-3/2 ≤ -x-y ≤ 3/2
-5/2 ≤ 4x²y-x-y ≤ 5/2
l4x²Y-Y-xl ≤ 5/2
l4x²Y-Y-xl ≤ 17/16
-1/2 ≤ x ≤ 1/2 et -1 ≤ y ≤ 1
0 ≤ x² ≤ 1/4
0 ≤ 4x² ≤ 1
-1 ≤ 4x²y ≤ 1
-3/2 ≤ x+y ≤ 3/2
-3/2 ≤ -x-y ≤ 3/2
-5/2 ≤ 4x²y-x-y ≤ 5/2
l4x²Y-Y-xl ≤ 5/2
l4x²Y-Y-xl ≤ 17/16