Bonjour,
(x+6)² = x² + 2×x×6 + 6² = x² + 12x + 36
(x+4)² = x² + 2×x×4 + 4² = x² + 8x + 16
(x-5)² = x² - 2×x×5 + 5² = x² - 10x + 25
(x-7)² = x² - 2×x×7 + 7² = x² - 14x + 49
(y-8)² = y² - 2×y×8 + 8² = y² - 16y + 64
(x+5)(x-5) = x² - 5² = x² - 25
(x+9)(x-9) = x² - 9² = x² - 81
(12+y)(12-y) = 12² - y² = 144 - y²
