Réponse :
Explications étape par étape :
a)
x + y = 6
x*y =72
9 * 8 =72 12 * 6 =72 et 12 *(-6)= -72
x + y = 6 => 12+(-6) = 6
x*y = -72 => 12 * (-6) = -72
b)
x + y = -21
x*y = 90 90 = 9 * 10 90 = 3 * 30 90 = 6 * 15 et 90 = (-6)*(-15)
x + y = 21 => -6 + (-15) = -21
x*y = -6 * (-15) = 90
c)
x + y = -56
x/y= -5 70 = 5*14 => 70/14 = 5 => -70/14 = -5
x + y = -56 => -70+14 = -56
x/y = -70/14 = -5
d)
x - y = -15
x*y= 126 126 = 3*42 126 = 7*18 126 = 6*21
x - y = -15 => 6 - 21 = -15
x*y = 6*21 = 126
