Math Problem Statement

The graph shows a sequence. What are the explicit and recursive forms of the sequence?

Solution

The graph in the image shows a sequence of points. Let's analyze the sequence step by step to determine both the explicit and recursive forms.

Step 1: Analyze the points

Looking at the graph, the points for the sequence correspond to the following values:

  • When x=1x = 1, y=5y = 5
  • When x=2x = 2, y=7y = 7
  • When x=3x = 3, y=9y = 9
  • When x=4x = 4, y=11y = 11
  • When x=5x = 5, y=13y = 13

These values correspond to the terms of the sequence:

  • a1=5a_1 = 5
  • a2=7a_2 = 7
  • a3=9a_3 = 9
  • a4=11a_4 = 11
  • a5=13a_5 = 13

Step 2: Find the pattern

We can observe that the sequence increases by a constant value of 2:

  • a2a1=75=2a_2 - a_1 = 7 - 5 = 2
  • a3a2=97=2a_3 - a_2 = 9 - 7 = 2
  • a4a3=119=2a_4 - a_3 = 11 - 9 = 2
  • a5a4=1311=2a_5 - a_4 = 13 - 11 = 2

This means the sequence is arithmetic with a common difference of 2.

Step 3: Determine the explicit form

The explicit form of an arithmetic sequence is given by: an=a1+(n1)da_n = a_1 + (n - 1)d where dd is the common difference and a1a_1 is the first term.

Substituting a1=5a_1 = 5 and d=2d = 2: an=5+(n1)2=5+2n2=2n+3a_n = 5 + (n - 1)2 = 5 + 2n - 2 = 2n + 3

So, the explicit form is an=2n+3a_n = 2n + 3.

Step 4: Determine the recursive form

The recursive form of an arithmetic sequence is: a1=5,an=an1+2forn>1a_1 = 5, \quad a_n = a_{n-1} + 2 \quad \text{for} \quad n > 1

Step 5: Conclusion

The explicit and recursive forms of the sequence are:

  • Explicit: an=2n+3a_n = 2n + 3
  • Recursive: a1=5,an=an1+2forn>1a_1 = 5, \, a_n = a_{n-1} + 2 \, \text{for} \, n > 1

Thus, the correct answer is Option B.


Would you like more details on any step or further explanations?

Here are 5 related questions to explore:

  1. How can we generalize explicit and recursive forms for different types of sequences?
  2. What is the formula for the nn-th term of a geometric sequence?
  3. How do you determine the common difference or ratio in a sequence?
  4. Can a sequence be both arithmetic and geometric at the same time?
  5. How do recursive sequences model real-world situations?

Tip: When identifying a sequence, always check if the differences between terms are constant for arithmetic or if the ratios between terms are constant for geometric sequences.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Recursive Sequences

Formulas

Explicit form of an arithmetic sequence: a_n = a_1 + (n - 1)d
Recursive form of an arithmetic sequence: a_1 = initial value, a_n = a_(n-1) + d

Theorems

Arithmetic sequence formula

Suitable Grade Level

Grades 8-10