Помогите (2a-3b+a) * (7a-b) (d-2c) * 5+8c

1) (2 * a - 3 * b + a) * (7 * a - b) = (3 * a - 3 * b) * (7 * a - b) = 3 * a * 7 * a - 3 * a * b - 3 * b * 7 * a + 3 * b * b = 21 * a ^ 2 - 3 * a * b - 21 * b * a + 3 * b ^ 2 = 21 * a ^ 2 - a * b * (3 + 21) + 3 * b ^ 2 = 21 * a ^ 2 - a * b * 24 + 3 * b ^ 2 = 3 * (7 * a ^ 2 - 8 * a * b + b ^ 2);

2) (d - 2 * c) * 5 + 8 * c = 5 * d - 2 * с * 5 + 8 * с = 5 * d - 10 * c + 8 * c = 5 * d - c * (10 - 8) = 5 * d - c * 2 = 5 * d - 2 * c;

То есть получили, (d - 2 * c) * 5 + 8 * c = 5 * d - 2 * c.