8): y = x²-6x21 – 36.

8) $$y = x^9 - 6x^{21} - 36$$

Находим производную:

$$y' = (x^9 - 6x^{21} - 36)' = (x^9)' - (6x^{21})' - 36' = 9x^8 - 6 \cdot 21 x^{20} - 0 = 9x^8 - 126x^{20}$$

Ответ: $$y' = 9x^8 - 126x^{20}$$