📚 What is the Common Difference?
In simple terms, the common difference is the constant value added or subtracted in an arithmetic sequence. An arithmetic sequence is a list of numbers where the difference between any two consecutive terms is always the same. Think of it like climbing stairs where each step is the same height!
🧮 How to Calculate the Common Difference
To find the common difference ($d$), simply subtract any term from the term that follows it. Here's the formula:
$d = a_{n} - a_{n-1}$
Where:
- 🔢 $d$ is the common difference
- 📈 $a_{n}$ is any term in the sequence
- 📉 $a_{n-1}$ is the term before $a_{n}$
✍️ Step-by-Step Example
Consider the arithmetic sequence: 2, 5, 8, 11, 14...
- Choose two consecutive terms: Let's pick 5 and 2.
- Subtract the first term from the second term: $5 - 2 = 3$
- Verify with another pair: Let's try 11 and 8. $11 - 8 = 3$
So, the common difference ($d$) is 3.
🆚 Common Difference vs. Common Ratio
It's easy to mix up common difference with common ratio. Let's clear up the confusion!
| Feature | Common Difference | Common Ratio |
|---|
| Definition | ➕ The constant value added/subtracted in an arithmetic sequence. | ➗ The constant value multiplied/divided in a geometric sequence. |
| Sequence Type | ➕ Arithmetic Sequence (e.g., 2, 4, 6, 8...) | ➗ Geometric Sequence (e.g., 2, 4, 8, 16...) |
| Calculation | ➖ Subtract a term from its subsequent term. | ➗ Divide a term by its preceding term. |
| Formula | $d = a_{n} - a_{n-1}$ | $r = \frac{a_{n}}{a_{n-1}}$ |
🚀 Key Takeaways
- ➕ Common Difference: Applies to arithmetic sequences.
- ➖ Calculation: Subtraction between consecutive terms.
- ➗ Common Ratio: Applies to geometric sequences (multiplication/division).