Finding the sum or an arithmetic series using summation notation

The video tutorial explains how to find the sum of a sequence using a specific formula. It begins with an introduction to the sum formula, followed by a breakdown of the problem and the notation involved. The teacher then demonstrates how to apply the formula to find the first and last terms of a sequence. Finally, the video provides a step-by-step guide to calculating the sum, including simplifying fractions and multiplying terms.

Explain how to calculate the sum of the first three terms of a sequence.

What steps are involved in multiplying a fraction by a whole number as mentioned in the lesson?