Question

Свойства арифметической прогресси

Answer 1

a₁ = 17                   a₂ = 21       a₁₀ = ?        a₂₀ = ?
a₂ = a₁ + d
d = a₂ - a₁ = 21 - 17 = 4
a₁₀ = a₁ + 9d = 17 + 9 * 4 = 17 + 36 = 53
a₂₀ = a₁ + 19d = 17 + 19 * 4 = 17 + 76 = 93
Ответ: 53 , 93