a² - b² = (a - b)(a + b)
a = 2x - y
b = 3x + 4y
(2x - y)² - (3x + 4y)² = (2x - y + 3x + 4y)(2x - y - 3x - 4y) = (5x + 3y)(-x - 5y) = -(5x + 3y)(x + 5y)
a² - b² = (a - b)(a + b)
a = 2x - y
b = 3x + 4y
(2x - y)² - (3x + 4y)² = (2x - y + 3x + 4y)(2x - y - 3x - 4y) = (5x + 3y)(-x - 5y) = -(5x + 3y)(x + 5y)