Дано функцию f (x) = x в квдрате-9x+20. Найдите значение x при которых: 1. f (x) = 0 2. f (x) = 20 3. f (x) = 12 3. f (x) = 30

1. x^{2} - 9x + 20 = 0

x1, 2 = (9 + - / sqrt{81 - 80}) / 2; x1 = 4; x2 = 5

2. x^{2} - 9x = 0; x = 9

3. x^{2} - 9x + 20 = 12

x^{2} - 9x + 6 = 0

x1, 2 = (9 + - / sqrt{81 - 24}) / 2; x1 / approx 0.73; x2 / approx 8.27

4. x^{2} - 9x - 10 = 0

x1, 2 = (9 + - / sqrt{81 + 40}) / 2; x1 = 10; x2 = 5