bjr
Soit B = (5x – 2)² + (5x – 2)(3x + 7)
1) Développer, réduire et ordonner B.
(5x – 2)² + (5x – 2)(3x + 7) =
(5x)² - 2*5x*2 + 2² + 5x*3x + 5x*7 - 2*3x - 2x7=
25x² - 20x + 4 + 15x² + 35x - 6x - 14 =
25x² + 15x²- 20x + 35x - 6x + 4 - 14 =
40x² + 9x² - 10
2) si on demande de factoriser
(5x – 2)² + (5x – 2)(3x + 7) =
(5x – 2)(5x - 2) + (5x – 2)(3x + 7)
=
(5x – 2)(5x - 2) + (5x – 2)(3x + 7)
=
(5x – 2)[(5x - 2) + (3x + 7)
] =
(5x - 2)(8x + 5)
