## Reflection: Complex Tasks Arithmetic Sequences - Section 1: Launch and Explore

The most common conversation that took place while students were working on the task worksheet centered on how many terms each sequence has. The two common strategies are outlined below.

1. Many students found the explicit formula for the nth term of the sequence and then set the final term equal to the formula and solved for n. This seemed to really make sense to students once we talked about this for our whole class discussion.

2. Another approach was to divide the difference of the first and last term by the common difference and then add one. This group tried this strategy but forgot to add the one at the end (their corrected work is shown in the photo). I heard them talking about this and I intervened because I thought this was a misconception that may go unnoticed. I gave them a simple sequence of 2, 4, 6, 8 and asked them to try that method and they realized that they needed to add 1 to get the correct number of terms.

Complex Tasks: How Many Terms are There?

# Arithmetic Sequences

Unit 9: Sequences and Series
Lesson 4 of 18

## Big Idea: Formalize arithmetic sequences by moving to formulas.

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Subject(s):
Math, Precalculus and Calculus, Geometry, Algebra 2, arithmetic sequence, Sequences and Series, partial sum
50 minutes

### Tim Marley

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