(-1,2)²)⁻¹ = (1,44)⁻¹= (144/10)⁻¹= 10/144= 5/72
((-1,2)²)⁻¹ = (-1,2)⁻² = 1/1,44
((-1,2)²)⁻¹ = (-10/12) do pot.2 = ( - 25/36)