Bonsoir,
1)
1- A = (7x - 3)² - 9
A = 49x² - 42x + 9 - 9
A = 49x² - 42x
2- A = (7x - 3)² - 9
A = (7x - 3 - 3) (7x - 3 + 3)
A = 7x (7x - 6)
3- 7x = 0 ou 7x - 6 = 0
x = 0 7x = 6
x = 6/7
2)
1- B = (x - 3)² - (x - 3) (1 - 2x)
B = (- 3 - 3)² - (- 3 - 3) (1 - 2 * - 3)
B = (- 6)² - (- 6) (1 + 6)
B = 36 - (- 6) * 7
B = 36 + 42
B = 78
2- B = (x - 3)² - (x - 3) (1 - 2x)
B = x² - 6x + 9 - (x - 2x² - 3 + 6x)
B = x² - 6x + 9 - x + 2x² + 3 - 6x
B = 3x² - 13x + 12.
3- B = (x - 3)² - (x - 3) (1 - 2x)
B = (x - 3) [(x - 3) - (1 - 2x)]
B = (x - 3) (x - 3 - 1 + 2x)
B = (x - 3) (3x - 4)
4- B = (x - 3) (3x - 4) = 0
x - 3 = 0 ou 3x - 4 = 0
x = 3 3x = 4
x = 4/3
3)
1- E = (2x + 3)² - x (2x + 3)
E = 4x² + 12x + 9 - 2x² - 3x
E = 2x² + 9x + 9
2- E = (2x + 3)² - x (2x + 3)
E = (2x + 3) [(2x + 3) - x]
E = (2x + 3) (x + 3)
3- E = 2x² + 9x + 9
E = 2 * - 2/3² + 9 * - 2/3 + 9
E = 2 * - 4/9 - 18/3 + 9
E = - 8/9 - 54/9 + 81/9
E = 19/9.
