Question

Дана арифметическая прогрессия (an). Известно, что a1=1,9 и d=1,5. Вычисли сумму первых семи членов арифметической прогрессии. Запиши ответ в виде числа, при необходимости округлив его до десятых

Answer 1

Ответ:

44,8

............

Answer 2

To find the sum of the first seven terms of an arithmetic progression, we can use the formula:

Sn = (n/2)(2a1 + (n-1)d)

where Sn is the sum of the first n terms, a1 is the first term, and d is the common difference.

In this case, we are given that a1 = 1.9 and d = 1.5. We need to find the sum of the first seven terms, so n = 7.

Plugging in the values into the formula, we get:

S7 = (7/2)(2(1.9) + (7-1)(1.5))

Calculating this expression, we find:

S7 = (7/2)(3.8 + 6(1.5))

S7 = (7/2)(3.8 + 9)

S7 = (7/2)(12.8)

S7 = 7(6.4)

S7 = 44.8

Therefore, the sum of the first seven terms of the arithmetic progression is approximately 44.8 when rounded to the nearest tenth.