(a - 8)² = a² - 16a + 64
(2x + 3)² = 4x² + 12x + 9
(y + 7)² = y² + 14y + 49
(x - 5y)² = x² - 10xy + 25y²
(x - 4)(x + 4) = x² - 16
(4a - b)(4a + b) = 16a² - b²
x² - 16 = (x - 4)(x + 4)
y² - 100 = (y - 10)(y + 10)
c² - 0,25 = c² - 0,5² = (c - 0,5)(c + 0,5)