Math Problem Statement

Find the next 2 terms for the sequences: (i) 1, 4, 7, 10, 13... (ii) 2, 6, 18, 54... (iii) 1, 3, 4, 7, 18, 29, 47...

Solution

Let's analyze the sequences in the image and determine the next two terms for each.


Sequence (i): 1, 4, 7, 10, 13...

This sequence has a constant difference of 3 between consecutive terms, making it an arithmetic progression.

  • Formula: an=a1+(n1)da_n = a_1 + (n-1)d, where a1=1a_1 = 1 and d=3d = 3.

The next two terms after 1313 are: 13+3=1613 + 3 = 16 16+3=1916 + 3 = 19

So, the next terms are 16, 19.


Sequence (ii): 2, 6, 18, 54...

Each term is obtained by multiplying the previous term by 33, making it a geometric progression.

  • Formula: an=a1rn1a_n = a_1 \cdot r^{n-1}, where a1=2a_1 = 2 and r=3r = 3.

The next two terms after 5454 are: 543=16254 \cdot 3 = 162 1623=486162 \cdot 3 = 486

So, the next terms are 162, 486.


Sequence (iii): 1, 3, 4, 7, 18, 29, 47...

This sequence does not follow a straightforward arithmetic or geometric pattern. Let's analyze differences between terms:

  • Differences: 31=23 - 1 = 2, 43=14 - 3 = 1, 74=37 - 4 = 3, 187=1118 - 7 = 11, 2918=1129 - 18 = 11, 4729=1847 - 29 = 18.

Observations: The differences appear to alternate between a smaller number (2, 1, 3) and a larger one (11, 18). We need more context for the pattern.

Can you clarify or confirm if the differences are alternating in pairs? If yes, the next differences would follow 1111 and 1818, making the next terms: 47+11=5847 + 11 = 58 58+18=7658 + 18 = 76

Next terms may be 58, 76. Let me know if this matches what you expect!


Would you like further clarification or details on any part? 😊


Related Questions:

  1. How can arithmetic and geometric progressions be represented graphically?
  2. What is the difference between arithmetic, geometric, and recursive sequences?
  3. Could the third sequence be generated by a recursive formula?
  4. How do you derive general formulas for unknown sequences?
  5. Are there real-world applications of such sequences in physics or economics?

Tip:

For mixed patterns (like in sequence iii), analyzing differences or ratios between terms often reveals hidden structures.

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Math Problem Analysis

Mathematical Concepts

Arithmetic Progression
Geometric Progression
Sequence Analysis

Formulas

Arithmetic progression formula: a_n = a_1 + (n-1)d
Geometric progression formula: a_n = a_1 * r^(n-1)

Theorems

Arithmetic and geometric sequence properties

Suitable Grade Level

Grades 8-10