a) (x + 11)² - (x - 9)² = (x - 11 - x + 9)(x - 11 + x - 9) = - 2(2x - 20) = 40 - 4x
b) (3x - 8y)² + 48xy = 9x² - 48xy + 64y² + 48xy = 9x² + 64y²
a) (x + 11)² - (x - 9)² = (x - 11 - x + 9)(x - 11 + x - 9) = - 2(2x - 20) = 40 - 4x
b) (3x - 8y)² + 48xy = 9x² - 48xy + 64y² + 48xy = 9x² + 64y²