Question

4,5 и 6 задание. Даю 33 Балла!

Answer 1

Ответ:

(см. объяснение)

Объяснение:

• 4-ое задание:

${x}^{2} + 6x + 5 = {x}^{2} + 5x + x + 5 = x(x + 5) + (x + 5) = (x + 5)(x + 1)$

• 5-ое задание:

$\frac{ { x }^{2} + 3x}{5} = \frac{ 5x - {x}^{2} }{2} \\ 2 {x}^{2} + 6x = 25x - 5 {x}^{2} \\ 7 {x}^{2} - 19x = 0 \\ x(7x - 19) = 0 \\ x = 0 \\ x = \frac{19}{7}$

• 6-ое задание:

$(x + 5)(x + 3) = 1.6 \times {x}^{2} \\ {x}^{2} + 8x + 15 - 1.6 {x}^{2} = 0 \\ 6 {x}^{2} - 80x - 150 = 0 \\ 3 {x}^{2} - 40x - 75 = 0 \\ 3 {x}^{2} + 5x - 45x - 75 = 0 \\ x(3x + 5) - 15(3x + 5) = 0 \\ (3x + 5)(x - 15) = 0 \\ x = 15 \\ = > \\ a = 20 \\ b = 18 \\ (20 + 18) \times 2 = 76$