Bonjour,
A=(5x-3)(2x-7)-(2x-7)²
developper et reduire A
A=(5x-3)(2x-7)-(2x-7)²
A = 10x² - 35x - 6x + 21 - (4x² - 28x + 49)
A = 10x² - 35x - 6x + 21 - 4x² + 28x - 49
A = 6x² - 13x - 28
factoriser A
A=(5x-3)(2x-7)-(2x-7)²
A = (2x - 7) [(5x - 3) - (2x - 7)]
A = (2x - 7) (5x - 3 - 2x + 7)
A = (2x - 7) (3x + 4)
calculer A pour x=2
A = 6x² - 13x - 28
A = 6 * 2² - 13 * 2 - 28
A = 6 * 4 - 26 - 28
A = 24 - 54
A = - 30
puis pour x=-1
A = 6x² - 13x - 28
A = 6 * - 1² - 13 * - 1 - 28
A = 6 + 13 - 28
A = - 9.
resoudre l equation
(2x-7)(3x+4)=0
2x - 7 = 0 3x + 4 = 0
2x = 7 3x = - 4
x = 7/2 = 3,5 x = - 4/3.
