Решим задачу, заполнив таблицу, где требуется найти значения d, n и aₙ для арифметической прогрессии.
Дано: a₁ = 3, a₂ = 5, d = 5 - 3 = 2, n = 7
a₇ = 3 + 2 × (7 - 1) = 3 + 2 × 6 = 3 + 12 = 15
Дано: a₁ = 4, a₂ = 7, d = a₂ - a₁ = 7 - 4 = 3, n = 5
a₅ = a₁ + d × (n - 1) = 4 + 3 × (5 - 1) = 4 + 3 × 4 = 4 + 12 = 16
Дано: a₁ = 2, a₂ = -2, d = a₂ - a₁ = -2 - 2 = -4, n = 8
a₈ = a₁ + d × (n - 1) = 2 + (-4) × (8 - 1) = 2 + (-4) × 7 = 2 - 28 = -26
Дано: a₁ = -1, a₂ = 5, d = a₂ - a₁ = 5 - (-1) = 6, n = 10
a₁₀ = a₁ + d × (n - 1) = -1 + 6 × (10 - 1) = -1 + 6 × 9 = -1 + 54 = 53
Дано: a₁ = -10, a₂ = -5, d = a₂ - a₁ = -5 - (-10) = 5, n = 6
a₆ = a₁ + d × (n - 1) = -10 + 5 × (6 - 1) = -10 + 5 × 5 = -10 + 25 = 15
Дано: a₁ = 12, d = 5, n = 14
a₂ = a₁ + d = 12 + 5 = 17
a₁₄ = a₁ + d × (n - 1) = 12 + 5 × (14 - 1) = 12 + 5 × 13 = 12 + 65 = 77
Дано: a₁ = 15, d = 3, n = 22
a₂ = a₁ + d = 15 + 3 = 18
a₂₂ = a₁ + d × (n - 1) = 15 + 3 × (22 - 1) = 15 + 3 × 21 = 15 + 63 = 78
Дано: a₂ = 11, d = 7, n = 16
a₁ = a₂ - d = 11 - 7 = 4
a₁₆ = a₁ + d × (n - 1) = 4 + 7 × (16 - 1) = 4 + 7 × 15 = 4 + 105 = 109
Дано: a₂ = -12, d = -3, n = 27
a₁ = a₂ - d = -12 - (-3) = -9
a₂₇ = a₁ + d × (n - 1) = -9 + (-3) × (27 - 1) = -9 + (-3) × 26 = -9 - 78 = -87
Дано: a₁ = 0.4, a₂ = 1.1, d = a₂ - a₁ = 1.1 - 0.4 = 0.7, n = 11
a₁₁ = a₁ + d × (n - 1) = 0.4 + 0.7 × (11 - 1) = 0.4 + 0.7 × 10 = 0.4 + 7 = 7.4
Заполненная таблица:
| № | a₁ | a₂ | d | n | aₙ |
|---|---|---|---|---|---|
| 1 | 3 | 5 | 2 | 7 | 15 |
| 2 | 4 | 7 | 3 | 5 | 16 |
| 3 | 2 | -2 | -4 | 8 | -26 |
| 4 | -1 | 5 | 6 | 10 | 53 |
| 5 | -10 | -5 | 5 | 6 | 15 |
| 6 | 12 | 17 | 5 | 14 | 77 |
| 7 | 15 | 18 | 3 | 22 | 78 |
| 8 | 4 | 11 | 7 | 16 | 109 |
| 9 | -9 | -12 | -3 | 27 | -87 |
| 10 | 0.4 | 1.1 | 0.7 | 11 | 7.4 |
Ответ: смотри таблицу выше.