1) x + 4y + x² - 16y² = x + 4y + (x - 4y)(x + 4y) = (x + 4y)*(x+ 1 - 4y).
2) 4x² - y² - 4x + 1 = 4x² - 4x + 1 - y² = (2x - 1)² - y² = (2x - 1 - y)*(2x - 1 + y).
1) x + 4y + x² - 16y² = x + 4y + (x - 4y)(x + 4y) = (x + 4y)*(x+ 1 - 4y).
2) 4x² - y² - 4x + 1 = 4x² - 4x + 1 - y² = (2x - 1)² - y² = (2x - 1 - y)*(2x - 1 + y).