pouvez vous maidez a faire tout lexercice 140 svp ​

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Ce n'est pas le 140 mais le 130 !

1)

A = (3/5 - 1/2) x 5/2

A = [(3 x 2) / (5 x 2) - (1 x 5)  (2 x 5)] x 5/2

A = (6/10 - 5/10) x 5/2

A = 1/10 x 5/2

A = 5/20

A = (5 x 1) / (5 x 4)

A = 1/4

B = (3 - 2/3) / (4/3 x 7)

B = [(3 x 3) / (1 x 3) - 2/3] : 28/3

B = (9/3 - 2/3) : 28/3

B = 7/3 : 28/3

B = 7/3 x 3/28

B = 21/84

B  = (21 x 1) / (21 x 4)

B  = 1/4

A = B

2)

C = 8/3 - 2/3 : 8/7

C = 8/3 - 16/21

C = (8 x 7) / (3 x 7) - 16/21

C = 56/21 - 16/21

C = 30/21

C = (3 x 10) / (3 x 7)

C = 10/7

D = (- 2/5 + 5/2) : (- 3/4 + 1/2)

D = [(- 2 x 2) / (5 x 2) + (5 x 5) / (2 x 5)] : [- 3/4 + (1 x 2) / (2x 2)]

D = (- 4/10 + 25/10) : (- 3/4 + 2/4)

D = 21/10 : (- 1/4)

D = 21/10 x - 4

D = - 84/10

D = (2 x - 42) / (2 x 5)

D = - 42/5.

3) L'inverse de B est 4 et l'opposé de D est 42/5.

4)

B + D = 1/4 - 42/5 = (1 x 5) / (4 x 5) - (42 x 4) / (5 x 4) = 5/20 - 168/20 = - 163/20

C x D = 10/7 x (- 42/5) = - 420/35 = (35 x - 12) / (35 x 1) = - 12

C/B = 10/7 : 1/4 = 10/7 x 4 = 40/7.