Помогите пожалуйста Б) (a-2b)^5

Решите задачу:

${(a - 2b)}^{5} = {(a - b)}^{3} \times {(a - b)}^{2} = ( {a}^{3} - 6 {a}^{2} b + 12a {b}^{2} - 8 {b}^{3} ) \times ( {a}^{2} - 4ab + 4 {b}^{2} ) = {a}^{5} - 4 {a}^{4} b + 4 {a}^{3} {b}^{2} - 6 {a}^{4} b + 24 {a}^{3} {b}^{2} - 24 {a}^{2} {b}^{3} + 12 {a}^{3} {b}^{2} - 48 {a}^{2} {b}^{3} + 48a {b}^{4} - 8 {a}^{2} {b}^{3} + 32a {b}^{4} - 32 {b}^{5} = {a}^{5} - 10 {a}^{4} b + 40 {a}^{3} {b}^{2} - 80 {a}^{2} {b}^{3} + 80a {b}^{4} - 32 {b}^{5}$