Question

Помогите с 11 по 15, пожалуйста, 14 не надо

Answer 1

Ответ:

11.

$y = 4 {x}^{2} - 7x - 2$

$y = 0 \\ 4 {x}^{2} - 7x - 2 = 0 \\ D = 49 + 32 = 81 \\ x_1 = \frac{7 + 9}{8} = 2 \\ x_2 = - \frac{2}{8} = - 0.25$

12.

$(5 - 3i)(1 + i) - 2i {}^{2} = 5 + 5i - 3i - 3i {}^{2} - 2 {i}^{2} = \\ = 5 + 2i - 5 {i}^{2} = 5 + 2i + 5 = 10 + 2i$

13.

$f(x) = 5 {x}^{3} + 3x + 1 \\ f( - x) = 5 {( - x)}^{3} - 3 x+ 1 = \\ = - 5 {x}^{3} - 3x + 1 = - (5 {x}^{3} + 3x - 1)\ne \: f(x)$

Функция нечетная

15.

$y = \sqrt{2x + 5} \\ \\ 2x + 5 \geqslant 0 \\ x \geqslant - 2.5 \\ \\ D(y):x\in[ - 2.5; + \infty )$