bx - by - x - y - ax - ay = b(x - y) - (x + y) - a(x + y)bx - by - x - y - ax - ay = (b - 1)(x - y) - (a + 1)(x + y)
bx - by - x - y - ax - ay = b(x - y) - (x + y) - a(x + y)
bx - by - x - y - ax - ay = (b - 1)(x - y) - (a + 1)(x + y)