Пошаговый ответ:
9х² + bx - 28 = 0
9 * (2/3)² + b * 2/3 = 28
9 * 4/9 + 2/3 * b = 28
4 + 2/3b = 28
2/3b = 24
b = 16
Пошаговый ответ:
9х² + bx - 28 = 0
9 * (2/3)² + b * 2/3 = 28
9 * 4/9 + 2/3 * b = 28
4 + 2/3b = 28
2/3b = 24
b = 16