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.