Помогите со множетелями.Заранее спасибо

4)
$12 x{y}^{2} - 4 {y}^{2} + 3 {x}^{2} y - xy = 4 {y}^{2} (3x - 1) + xy(3x - 1) = (3x - 1)(4 {y}^{2} + xy) =y (3x - 1)(4y + x)$
5)
$3 {x}^{3} - 5 {x}^{2} y - 9x + 15y = (3 {x}^{3} - 9x) - (5 {x}^{2}y - 15y) = 3x( {x}^{2} - 3) - 5y( {x}^{2} - 3) = ( {x}^{2} - 3)(3x - 5y)$
6)
${m}^{3} {n}^{3} - m + {m}^{2} {n}^{4} - n = m( {m}^{2} {n}^{3} - 1) + n( {m}^{2} {n}^{3} - 1) = ( {m}^{2} {n}^{3} - 1)(m + n)$