The fourth term of the arithmetic progression is (-4.5). Find the sum of the second and sixth terms of this progression.

| April 25, 2021 | education

Let’s use the formula of the nth term of the arithmetic progression an = a1 + (n – 1) * d, where a1 is the first term of the arithmetic progression, d is the difference of the arithmetic progression.

According to the condition of the problem, in this arithmetic progression, the fourth term a4 = -4.5.

Applying the formula for the nth term of the arithmetic progression with n = 4, we get:

a1 + (4 – 1) * d = a1 + 3 * d = -4.5.

Applying the formula for the nth term of the arithmetic progression for n = 2 and n = 6, we write the sum of the second and sixth terms of this progression:

a2 + a6 = a1 + (2 – 1) * d + a1 + (6 – 1) * d = a1 + d + a1 + 5 * d = 2 * a1 + 6 * d = 2 * (a1 + 3 * d ) = 2 * -4.5 = -9.

Answer: the sum of the second and sixth terms of this progression is -9.



One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.