Даю 50 баллов 2а(5-2а) - (а-2)(а+2) и тд

Ответ:

$a)2a(5 - a) - (a - 2)(a + 2) = \\ 10a - 2 {a}^{2} - ( {a}^{2} - 4) = \\ = 10a - 2 {a}^{2} - {a}^{2} + 4 = 10a - 3 {a}^{2} + 4$

$b)(x - 3)(x - 7) - 2x(3x - 5) = \\ = {x}^{2} - 10x + 21 - 6 {x}^{2} + 10x = \\ = 21 - 5 {x}^{2}$

$v)2 {(m + 1)}^{2} - 4m = \\ = 2( {m}^{2} + 2m + 1) - 4m = \\ = 2 {m}^{2} + 4m + 2 - 4m = \\ = 2 {m}^{2} + 2$

${( {y}^{2} - 2y) }^{2} - {y}^{2} (y + 3)(y - 3) + 2y(2 {y}^{2} + 5) = \\ = ( {y}^{4} - 4 {y}^{3} + 2 {y}^{2} ) - {y}^{2} ( {y}^{2} - 9) + 4 {y}^{3} + 10y = \\ = {y}^{4} - 4 {y}^{3} + 2 {y}^{2} - {y}^{4} + 9 {y}^{2} + 4 {y}^{3} + 10y = \\ = 10y + 11 {y}^{2}$