Long division of polynomials is the same as that of integers. We find the number that we can multiply (4x + 5y) by to obtain the given polynomial. This is (4x - 5y). Moreover, this is visible from the fact that (16x² - 25y²) satisfies the identity: (a² - b²) = (a + b)(a - b); where a = 4x and b = 5y
