Помогите пожалуйста я дам 20б.

2)
$- {a}^{4} (7 {a}^{2} + 3) + 7 {a}^{6} = - 7 {a}^{4 + 2} - 3 {a}^{4} + 7 {a}^{6} = - 7 {a}^{6} - 3 {a}^{4} + 7 {a}^{6} = - 3 {a}^{4}$
При a = -1/2:
$- 3 {a}^{4} = - 3 \times ( \frac{1}{2} )^{4} = - 3 \times \frac{1}{16} = - \frac{3}{16}$
6)
$\frac{2x + 3}{2} = \frac{3x - 4}{4} - 5 \\ \frac{10(2x + 3)}{20} = \frac{5(3x - 4)}{20} - \frac{100}{20} \\ 10(2x + 3) = 5(3x - 4) - 100 \\ 20x + 30 = 15x - 20 - 100 \\ 20x - 15x = - 20 - 100 - 30 \\ 5x = - 150 \\ x = - 30$