bonjour,
756 = 2 x 358 = 2 x 2 x 189 = 2 x 2 x 3 x 63 = 2 x 2 x 3 x 3 x 3 x 7
945 = 3 x 315 = 3 x 3 x 105 = 3 x 3 x 3 x 35 = 3 x 3 x 3 x 5 x 7
du coup, -756/945 = -(2 x 2 x 3 x 3 x 3 x 7)/(3 x 3 x 3 x 5 x 7)
après simplification il reste : - (2x2)/5 = -4/5
Bonne soirée,
T.
