a) (x+ 1)+ x(x + 1) = (x + 1)(1 + x)
б) m²(n + 1) + 2m(n +1) = (n + 1)(m² + 2m) = m(n + 1)(m + 2)
в) y(a - y) - y²(a - y) = (a - y)(y - y²) = y(a - y)(1 - y)
г) a(a - 1) - (a - 1) = (a - 1)(a - 1)
