Find Missing Integers

In previous lessons you worked with arithmetic sequences. How to find a missing number in an arithmetic sequence:

Determine if the order of numbers is ascending (getting larger in value) or descending (becoming smaller in value).
Find the difference between numbers that are next to each other.
Use the difference between numbers to find the missing number.

In these lessons we continue with arithmetic sequences, but they may include negative integers.

Example: Find the missing number: 2, 1, ?, -1

The order of numbers is descending (going down).
The difference between numbers is 2 - 1 = 1
Since the order is descending subtract 1 - 1. The missing number may be 0.
The missing number is 0 since subtracting another 1 results in the last number -1.

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