Exercice 7. Factoriser les expressions suivantes. A= x² – 49 B = 4x² – 25 C = x2 – 22x + 121 D = 9x2 + 30x + 25. Exercice 8. Factoriser les expressions suivante

Bonsoir,

Exercice 7. Factoriser les expressions suivantes.

A= x² – 49  

A = (x - 7) (x + 7)

B = 4x² – 25  

B = (2x - 5) (2x + 5)

C = x² – 22x + 121

C = (x - 11)²

D = 9x² + 30x + 25.

D = (3x + 5)²

Exercice 8. Factoriser les expressions suivantes.

A = (x – 3)² – 16

A = (x- 3 - 4) (x - 3 + 4)

A = (x - 7) (x + 1)

C = (3x – 7)² – (x + 2)²

C = (3x - 7 - x - 2) (3x - 7 + x + 2)

C = (2x - 9) (4x - 5)

B = 4(x - 1)² – 81

B = (2x - 11) (2x + 7)

D = (5 + x)² – 36x²

D = (5 + x - 6x) (5 - x + 6x)

D = (7x + 5) (5x + 5)

bonjour

ce sont toutes des identités remarquables  

A = x² - 49

  = ( x - 7 ) ( x + 7)

B = 4 x² - 25

  = (  2 x - 5 ) ( 2 x + 5)

C = x² - 22 x + 121

  = ( x - 11 )²

d = 9 x² + 30 x + 25

  = ( 3 x + 5 )²

A =  ( x - 3 - 4 ) ( x - 3 + 4)

  = ( x - 7 ) ( x + 1 )

C = ( 3 x - 7 + x + 2 ) ( 3 x - 7 - x - 2 )

  = ( 4 x - 5 ) ( 2 x - 9 )

B =   ( 4 x - 4 )² - 81

  = ( 4 x - 4 - 9 ) ( 4 x - 4 + 9 )

  = ( 4 x - 13 = ( 4 x + 5 )

D = ( 5 + x - 6 x ) ( 5 + x + 6 x)

   = ( - 5 x + 5 ) ( 7 x + 5 )

   = 5 ( - x + 1 ) ( 7 x + 5 )