Réponse :
Factoriser :
A = 3x² + 8x
A = x ( 3x + 8)
B = (2x - 1)(x - 2) + 4(2x - 1)
B = (2x - 1) ( x - 2 + 4 )
B = (2x - 1) (x + 2)
C = (2 - x ) (x + 5) + (3 + x ) (x + 5)
C = ( x + 5 ) ( 2 - x + 3 + x )
C = ( x + 5 ) 5
C = 5 ( x + 5)
22/ Factorisation
a) ( x + 1)(x + 6) + 4x(x+6)
(x + 6) (x + 1 + 4x)
( x + 6) ( 5x + 1)
b) ( 7x + 9)² + ( 7x + 9 ) (x + 5) ⇒ ( a + b)² = ( a + b)(a +b)
(7x + 9)(7x + 9) + (7x + 9)(x + 5)
(7x + 9 ) (7x + 9 + x + 5 )
( 7x + 9) ( 8x + 14)
(7x + 9 ) 2(4x + 7)
2(7x + 9 )( 4x + 7)
c) - 4( a - 2 ) - (b + 8)(a - 2 )
( a - 2) [ - 4 - (b + 8)]
( a - 2) ( - 4 - b - 8 )
( a - 2 ) ( - b - 12 )
d) (4b + 1 )(b - 8) - 8( 4b + 1)
( 4b + 1 ) ( b - 8 - 8 )
( 4b + 1 ) ( b - 16 )
e) - x² ( x+ 3 ) + ( x + 2)(x + 3 )
( x + 3) ( - x² + x + 2)
f) ( a + 4 ) ( 7 - a ) + ( 4a + 1) ( 7 - a )
( 7 - a ) ( a + 4 + 4a + 1 )
( 7 - a ) (5a + 5 )
( 7 - a ) 5(a + 1)
5(7 - a)(a + 1)
