Find the twentieth term of the arithmetic progress if a1 = – 8 and d = 2.

An arithmetic progression is a certain sequence of numbers in which each next term differs from the previous one by the same number d (which is called the step of the progression or the difference of the progression).

Given:

A1 = -8;

d = 2.

Find: A20.

Solution:

To calculate the twentieth term of a given arithmetic progression, we use the formula for the nth term of the progression (in this case, n = 20):

An = A1 + (n – 1) * d.

Let’s substitute the data into the formula and calculate:
A20 = -8 + (20 – 1) * (2) = 30.

Answer: A20 = 30.