Répondre :
(AB)²= ( 6 -2 )² + ( - 3 + 1 )² = 4 ² + ( - 2 )² = 16 + 4 = 20
( BC)² = ( - 1 - 6 )² + ( - 7 + 3 )² = ( - 7 )² + ( - 4 )² = 49 + 16 = 65
(AC)² = ( - 1 - 2 )² + ( - 7 + 1 )² = ( - 3 )² + ( - 6 )² = 9 + 36 = 45
45 + 20 = 65
donc il est rectangle en A