Bonsoir je suis en 4ème et je souhaiterais que vous m'aidiez pour un exercice de maths alors voilà : Merci !! Vraiment merci !

Bonsoir,

Exercice 1 :

b x c = -8 x 8 = -64
a + b x c = 9 - 64 = -55

b x c = 7 x -11 = -77
a + b x c = a - 77 = -80 donc a = - 80 + 77 = -3

b x c = -2 x -3 = 6
a + b x c = a + 6 = 0 donc a = -6

Exercice 2 :

A = 7/6 - 3/5 x 5/14
A = 7/6 - 5/5 x 3/14
A = 7/6 - 3/14 car 5/5 = 1
A = 7/(2 x 3) - 3/(2 x 7)
A = (7 x 7)/(6 x 7) - (3 x 3)/(3 x 14)
A = 49/42 - 9/42
A = 40/42
A = (2 x 20)/(2 x 21)
A = 20/21

B = (2/7 - 2/5) x 4/7
B = (10/35 - 14/35) x 4/7
B = (-4/35) x 4/7
B = -16/245

C = (3/4 - 8/7) x (3/14 - 1/2)
C = (21/28 - 32/28) x (3/14 - 7/14)
C = (-11/28) x (-4/14)
C = 4/28 x 11/14
C = 1/7 x 11/14
C = 11/98

D = (3/4 - 4/3) x 5
D = (9/12 - 16/12) x 5
D = (-7/12) x 5
D = (-35/12)