Bonjour pouvez vous m aidez sur l ex 5 Merci d avance

Bonjour ;

a.

A = ab + cd = 2/3 x (- 1/4) + 2/5 x (- 1/2)

= - 2/3 x 1/4 - 2/5 x 1/2

= - (2 x 1)/(3 x 4) - (2 x 1)/(5 x 2)

= - 2/12 - 2/10

= - 1/6 - 1/5

= - (1/6 + 1/5)

= - ((5 x 1)/(5 x 6) + (6 x 1)/( 5x 6))

= - (5/30 + 6/30)

= - (5 + 6)/30

= - 11/30 .

b.

On a : a + d = 2/3 - 1/2

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

= 4/6 - 3/6

= (4 - 3)/6 = 1/6 ;

et : b + c = - 1/4 + 2/5 = - (1 x 5)/(4 x 5) + (2 x 4)/(4 x 5)

= - 5/20 + 8/20

= (- 5 + 8)/20

= 3/20 ;

donc : (a + d)/(b + c) = (1/6)/(3/20) = 1/6 x 20/3

= (1 x 20)/(6 x 3)

= 20/18

= 10/9 .

Réponse :

Bonjour

Explications étape par étape

a = 2/3 b= -1/4 c = 2/5 et d= -1/2

A = ab +cd

A = 2/3 X -1/4 + 2/5 X -1/2

A = -2/12 -2/10

A = -2/12 X 10/10 -2/10 X 12/12

A = -20/120 -24/120

A = -44/120

A = -44/120 : 4/4 = -11/30

B = a + d = 2/3 + -1/2 = 2/3 X 2/2 -1/2 X 3/3   = 4/6 -3/6     = 1/6

     b + c    -1/4 + 2/5    -1/4 X 5/5 +2/5 X 4/4   -5/20 +8/20   3/20

B = 1/6 X 20/3

B = 20/18 : 2/2 = 10/9