Réponse:
(a+1)²-(a+7)² = [(a+1)+(a+7)]×[(a+1)-(a+7)]
(a+1)²-(a+7)² = (2a+8)(a+1-a-7)
(a+1)²-(a+7)² = (2a+8)×(-6)
(a+1)²-(a+7)² = -6× (2×a+2×4)
(a+1)²-(a+7)² = -12(a+4)
64x² + 128x + 64 = (8x)² + 2×8x×8 × 8²
64x² + 128x + 64 = (8x +8)²
(-6x+9)² - 4 = (-6x+9)² - 2²
(-6x+9)² - 4 = (-6x+9-2)(-6x+9+2)
(-6x+9)² - 4 = (-6x + 7)(-6x + 11)
