Bonsoir,
A = (x + 1)(2 - x) - 3(x + 1)²
Développer et réduire A:
A = (x + 1)(2 - x) - 3(x + 1)²
A = 2x - x² + 2 - x - 3(x + 1)²
A = -x² + x + 2 - 3(x + 1)²
→ identité remarquable :
A = -x² + x + 2 - 3(x² + 2x + 1)
A = -x² + x + 2- 3x² -6x - 3
A = -4x² - 5x - 1
Factoriser A :
A = (x + 1)(2 - x) - 3(x + 1)²
A = (x + 1)(2 - x) - 3(x + 1)(x + 1)
A = (x + 1)(2 - x - (3x + 3))
A = (x + 1)(2 - x - 3x - 3)
A = (x + 1)(-1 - 4x)
A = -(4x + 1)(x + 1)
Calculer A pour x = 1/4 :
A = -4x² - 5x - 1
A = -4*(1/4)² - 5*(1/4) - 1
A = -4*(1/16) - 5/4 - 1
A = -4/16 - 5/4 - 1
A = -1/4 - 5/4 - 4/4
A = -10/4
A = -2,5
* = multiplication
Bonne soirée.
