Question

(y + 7)3 - y3 - 21y2 > 0​

Answer 1

Объяснение:

(y+7)³-y³-21y²>0

y³+21y²+147y+343-y³-21y²>0 (Сокращаем y³ и -y³, 21y² и -21y²).

147y+343>0

147y>-343

y>-343/147

y>7/3

$y = 2 \frac{2}{3}$