Réponse :
Bonsoir
1) x² + 10x + 25 = x² + 2×5x + 5² = (x + 5)²
(identité remarquable a² + 2ab + b² = (a + b)²)
2) (x + 3)² - 8(x+1)² = (x + 3)² - [√8(x + 1)]² = [x + 3 - √8(x + 1)][x + 3 + √8(x + 1)]
= (x + 3 - x√8 - √8)(x + 3 + x√8 + √8)
(identité remarquable a² - b² = (a + b)(a - b)
3) 2x² + 7x = x(2x + 7)
4) 4(x + 1) + (x + 1)(x - 2) = (x + 1)(4 + x - 2) = (x + 1)(x + 2)
5) 9x² - 49 = (3x)² - 7² = (3x + 7)(3x - 7)
6) 25 - 10u + u² = (u + 5)²
