СРОЧНО напишите решение ПОДРОБНО номера 1,2и 7

1)
$4x + y = 2y - 4 \\ 3x + y = x + 1 \\ \\ 4x + y - 2y = - 4 \\ 3x - x + y = 1 \\ \\ 4x - y = - 4 \\ 2x + y = 1 \\ \\ 6x = - 3 \\ y = 1 - 2x \\ \\ x = - 0.5 \\ y = 1 - 2x\\ \\ x = - 0.5 \\ y = 1 - 2 \times ( - 0.5 )= 1 + 1 = 2$
Ответ: (-0,5; 2)

2)
$f(4) = \frac{ {4}^{2} - 2 \times 4 - 8}{ 4 + 2} = \frac{0}{6} = 0 \\ \\ f(0) = \frac{ {0}^{2} - 2 \times 0 - 8 }{0 + 2} = \frac{ - 8}{2} = - 4 \\ \\ f(3) = \frac{ {3}^{2} - 2 \times 3 - 8 }{3 + 2} = \frac{ - 5}{5} = - 1 \\ \\ 3f(4) - f(0) + 2f(3) = 3 \times 0 - ( - 4) + 2 \times ( - 1) = 4 - 2 = 2$
Ответ: 2.

7)
$(a - b)( {a}^{2} + ab + {b}^{2} ) + b {(a - b)}^{2} - a(a - b)(a + 2b) = {(a - b)}^{3} + b {(a - b)}^{2} - a(a - b)(a + 2b) = (a - b)( {(a - b)}^{2} + b(a - b) - a(a + 2b)) = (a - b)( {a}^{2} - 2ab + {b}^{2} + ab - {b}^{2} - {a}^{2} - 2ab) = (a - b)( - 3ab) = - 3 {a}^{2} b + 3a {b}^{2}$