Bonjour
1) Développer :
D = (2x + 1)² - (x - 3) (2x + 1)
D = 4x² + 4x + 1 - (2x² + x - 6x - 3)
D = 4x² + 4x + 1 - 2x² - x + 6x + 3
D = 4x² - 2x² + 4x + 6x - x + 1 + 3
D = 2x² + 9x + 4
2)
Pour x = -1/2
D = 2x² + 9x + 4
D = 2 * (- 1/2)² + 9 * (- 1/2) + 4
D = 2 * (1/4) - 9/2 + 4
D = 2/4 - 9/2 + 4
D = 1/2 - 9/2 + 8/2
D = 9/2 - 9/2
D = 0
Pour x = 0
D = 2x² + 9x + 4
D = 2 * 0² + 9 * 0 + 4
D = 4.
