1) a₁ = - 9 a₃ = - 23
a₃ = a₁ + 2d
2d = a₃ - a₁ = - 23 - (- 9) = - 23 + 9 = - 14
d = - 7
a₁₀ = a₁ + 9d = - 9 + 9 * (- 7) = - 9 - 63 = - 72
Ответ : Д
2) a₁ = - 2 a₇ = 16
a₇ = a₁ + 6d
6d = a₇ - a₁ = 16 - (- 2) = 16 + 2 = 18
d = 3
a₁₀ = a₁ + 9d = - 2 + 9 * 3 = - 2 + 27 = 25
Ответ : A
3) a₁ = - 5 a₁₃ = - 29
a₁₃ = a₁ + 12d
12d = a₁₃ - a₁ = - 29 - (- 5) = - 29 + 5 = - 24
d = - 2
a₁₀ = a₁ + 9d = - 5 + 9 * (- 2) = - 5 - 18 = - 23
Ответ : Г
4) a₁ = -1 a₁₄ = 51
a₁₄ = a₁ + 13d
13d = a₁₄ - a₁ = 51 - (- 1) = 51 + 1 = 52
d = 4
a₁₀ = a₁ + 9d = - 1 + 9 * 4 = - 1 + 36 = 35
Ответ : Б