Bonjour,
A = (x + 3)(-3x + 1) + (x + 3)(4x - 2)
A = (x + 3)(-3x + 1 + 4x - 2)
A = (x + 3)(x - 1)
B = (x + 1)² - (x - 2)²
B = (x + 1 + (x - 2))(x + 1 - (x - 2))
B = (x + 1 + x - 2)(x + 1 - x + 2)
B = (2x - 1)(3)
B = 3(2x - 1)
Identité remarquable :
a² - b² = (a + b)(a - b)
