А) 3x + 3y + a(x + y) = 3(x + y) + a(x + y) = (x + y)(3 + a)
б) 5a - c(a - b) - 5b = 5(a - b) - c(a - b) = (a - b)(5 - c)
в) ac - 2ad - x(c - 2d) = a(c - 2d) - x(c - 2d) = (c - 2d)(a - x)
г) 4ad - 3c(2a + 3x) + 6dx = 2d(2a + 3x) - 3c(2a + 3x) = (2a + 3x)(2d - 3c)
д) x³ + x + y(x² + 1) = x(x² + 1) + y(x² + 1) = (x² + 1)(x + y)
е) x² + xy + z(x + y) = x(x + y) + z(x + y) = (x + y)(x + z)