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Ответ:

[tex](7 - 2a)(4 {a}^{2} + 4a + 3) = 28 {a}^{2} + 28a + 21 - 8 {a}^{3} - 8 {a}^{2} - 6a = - 8 {a}^{3} + 20 {a}^{2} + 22a + 21[/tex]

[tex](3y - 4)( {y}^{2} - y + 1) = 3 {y}^{3} - 3 {y}^{2} + 3y - 4 {y}^{2} + 4y - 4 = 3 {y}^{3} - 7 {y}^{2} + 7y - 4[/tex]

[tex](3b - 2)(5 - 2b) + 6 {b}^{2} = 15b - 6 {b}^{2} - 10 + 4b + 6 {b}^{2} = 19b - 10[/tex]

[tex]5 {b}^{3} + ( {a}^{2} + 5b)(ab - {b}^{2} ) = 5 {b}^{3} + {a}^{3} b - {a}^{2} {b}^{2} + 5a {b}^{2} - 5 {b}^{3} = ab( {a}^{2} - ab + 5b)[/tex]

[tex](a - 7)(a + 5) + (a + 8)(a - 6) = {a}^{2} + 5a - 7a - 35 + {a}^{2} - 6a + 8a - 48 = 2 {a}^{2} - 83[/tex]

[tex]2 \times {( - 7)}^{2} - 83 = 98 - 83 = 15[/tex]