7y² + y = 0
y(7y + 1) = 0
y = 0 или 7y + 1 = 0
y = 0 или 7y = -1
y = 0 или y = -\frac{1}{7}
Проверка:
1) y = 0: 7 * 0² + 0 = 0 + 0 = 0
2) y = -\frac{1}{7}: 7 * (- \frac{1}{7})² - \frac{1}{7} = 7 * \frac{1}{49} - \frac{1}{7} = \frac{1}{7} - \frac{1}{7} = 0
Ответ: y₁ = 0, y₂ = -\frac{1}{7}