bonjour
A = ( x + 7 ) ( x + 1 - 1 ) = x ( x + 7 )
B = ( 2 x - 5 ) ( 2 x - 5 - x - 2 ) = ( 2 x - 5 ) ( x - 7 )
C = 1 ( 2 x + 1 ) + 5 x ( 2 x + 1 ) - 3 x ( 2 x + 1 )
C = ( 2 x + 1 ) ( 5 x - 3 x )
d = ( x - 8 ) ( x - 8 + 1 ) = ( x - 8 ) ( x - 7)
Réponse:
A=(x + 1) (x + 7) - (x + 7)
=(x × x + x × 7 ) + (1 × x + 1 × 7 ) - x + 7
= x² + 7x + x + 7 - x + 7
= x² + 7x + 14
B= (2 x – 5)2 - (2 x – 5) (x + 2)
= (2 × 2x - 2 × 5) - (2x × x + 2x × 2) - (5 × x + 5 × 2)
= 4x - 10 - 2x² + 4x - 5x + 10
= -2x² + 3x
C= 2 x + 1 + 5 x (2 x + 1) - 3 x (2 x + 1)
= 2x + 1 + (5 × 2x + 5 × 1) - (3 × 2x + 3 × 1)
= 2x + 1 + 10x + 5 - 6x + 3
= 6x + 9
D=(x - 8)2 + (x – 8)
= (2 × x - 2 × 8) + x - 8
= 2x - 16 + x - 8
= 3x - 24