Bonjour
1)
a. (5x + 3) (5x - 3) = 5x * 5x + 3 * - 3 = 25x² - 9
b. (7 + 8a)² = 7 * 7 + 7 * 8a * 2 + 8a * 8a = 49 + 112a + 64a²
c. (4f - 9g)² = 4f * 4f + 4f * - 9g * 2 - 9g * - 9g = 16f² - 72fg + 81g²
2)
a. x² - 36 = (x)² - (6)² = (x - 6) (x + 6)
b. 100 - 4x² = (10)² - (2x)² = (10 - 2x) (10x + 2x) = - 4(x - 5) (x + 5)
