Odpowiedź:
a)
(a + 2)(b + 1) = ab + 2b + a + 2 = a + ab + 2b + 2
b)
(2x + 1)(3 - y) = 6x + 3 - 2xy - y = 6x - 2xy - y + 3
c)
(x - 1)(a - b) = ax - a - bx + b = - a + ax - bx + b
d)
(2a - 1)(b - 3) = 2ab - b - 6a + 3 = - 6a + 2ab - b + 3
e)
(x + 1)(y - 2) = xy + y - 2x - 2 = - 2x + xy + y - 2
f)
(a + b)(x - y) = ax + bx - ay - by
