by+by-y-x-ay-ax Представьте многочлены в виде произведения

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

Ответ: (x + y) (b - a - 1).