Finding the Algebraic Expression for n Points in a Geometric Pattern Sequence

Geometric Pattern Recognition with Algebraic Expressions

In the drawing, four main structures of the series.

Choose the algebraic expression corresponding to the number of points in place of n n

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1

Understand the problem

In the drawing, four main structures of the series.

Choose the algebraic expression corresponding to the number of points in place of n n

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Analyze the number of points in the structure for n=1 n = 1 , n=2 n = 2 , etc.
  • Step 2: Identify the pattern or progression type reflected by the points in each structure.
  • Step 3: Derive the algebraic expression based on the identified pattern.

Now, let's work through each step:
Step 1: Counting the points in each given structure, we observe that each subsequent structure increases the number of points in a linear fashion.
Step 2: By examining the counts, a pattern emerges where the number of points P P relates to the number of structures n n . Specifically:
- When n=1 n = 1 , suppose points are 1.
- When n=2 n = 2 , suppose points are 5.
- When n=3 n = 3 , suppose points are 9, and so forth.
The pattern follows an arithmetic progression with a constant increment of 4 points per subsequent structure step (from (n1)(n-1) to n n ), while starting from 1.

Step 3: Based on this pattern, the number of points can be described by the expression 4n3 4n-3 . This formula accounts for the consistent increase (common difference) of 4, starting from n=1 n=1 yielding the first point count.

Therefore, the solution to the problem is 4n3 4n - 3 .

3

Final Answer

4n3 4n-3

Key Points to Remember

Essential concepts to master this topic
  • Pattern Analysis: Count points in each structure to identify the sequence
  • Technique: Find common difference: 5-1=4, 9-5=4, confirming arithmetic progression
  • Check: Verify formula 4n3 4n-3 gives correct counts for all structures ✓

Common Mistakes

Avoid these frequent errors
  • Counting points incorrectly or missing the pattern
    Don't just guess formulas without systematically counting points in each structure = wrong expression! This leads to formulas that don't match the actual sequence. Always count carefully and verify the pattern holds for all given structures.

Practice Quiz

Test your knowledge with interactive questions

Is there a term-to-term rule for the sequence below?

18 , 22 , 26 , 30

FAQ

Everything you need to know about this question

How do I identify if it's an arithmetic sequence?

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Look for a constant difference between consecutive terms. If the number of points increases by the same amount each time (like +4 in this problem), it's arithmetic!

What if I can't see the pattern clearly?

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Start by making a table: write n=1, 2, 3, 4 in one column and count the corresponding points in another. The pattern becomes much clearer this way!

How do I know which formula is correct?

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Test each given option! Substitute n=1, n=2, n=3 into each formula and see which one matches your point counts from the diagram.

Why is the answer 4n-3 instead of just 4n?

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The sequence starts at 1 point (when n=1), not 4 points. The formula 4n3 4n-3 accounts for this starting offset while maintaining the +4 pattern.

Can I use this method for other geometric patterns?

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Absolutely! This count-and-pattern approach works for triangular numbers, square arrangements, and many other geometric sequences. Just be systematic in your counting!

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