Bjr, aidez moi svp Factoriser : 49x² + 56x + 16 (-3x + 5) (5x + 9) - 7 (-3x + 5) 64x² + 48 x + 9 (2x + 8)² - 9 (8x + 3) (6x + 8) - (8x + 3) (4x + 3) (5x + 1) (2

bonjour,

49 x² + 56  x + 16  = ( 7 x + 4 )²

(-3 x + 5) (5 x + 9) - 7 (-3 x + 5)  

= ( - 3 x + 5 ) ( 5 x + 9 - 7 ) = ( - 3 x + 5 ) ( 5 x +  2)

64 x² + 48 x + 9  =  ( 8 x + 3 )²

(2 x + 8)² - 9  = ( 2 x + 8 - 3 ) ( 2 x + 8 + 3 ) = ( 2 x + 5 ) ( 2 x + 11 )

(8 x + 3) (6 x + 8) - (8 x + 3) (4 x + 3)

( 8 x + 3 ) ( 6 x + 8 - 4 x - 3 ) = ( 8 x + 3 ) ( 2 x + 5 )

(5 x + 1) (2 x + 3) + (5 x + 1) (x - 2) - (7 - 4) (10 x + 2)  

manque des inconnues  ( 7 - 4) ?

(a + 3)² - (a - 4)²

= ( a + 3 + a - 4) ( a + 3 - a + 4 ) = 7 ( 2 a - 1 )