Find the First Term Using the Sequence Formula 6n-1

Sequence Formula with Position Variable

A sequence has the rule 6n1 6n-1 .

What is the first term in the sequence?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the first term
00:03 Insert the position of the appropriate term in the formula and solve
00:16 Always solve multiplication and division before addition and subtraction
00:25 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

A sequence has the rule 6n1 6n-1 .

What is the first term in the sequence?

2

Step-by-step solution

To determine the first term in the sequence, we must evaluate the expression 6n1 6n - 1 at n=1 n = 1 since n n typically starts at 1 for sequences:

  • Step 1: Substitute n=1 n = 1 into 6n1 6n - 1 .
  • Step 2: Compute 6×11 6 \times 1 - 1 .
  • Step 3: Simplify the expression: 6×1=6 6 \times 1 = 6 .
  • Step 4: Subtract 1 from 6, giving us 5.

Therefore, the first term in the sequence is 5 5 .

Upon reviewing the answer choices, the correct choice is:
Choice 1: 5

3

Final Answer

5

Key Points to Remember

Essential concepts to master this topic
  • Rule: For first term, substitute n = 1 into formula
  • Technique: Calculate 6(1) - 1 = 6 - 1 = 5
  • Check: Verify by computing next terms: second term is 6(2) - 1 = 11 ✓

Common Mistakes

Avoid these frequent errors
  • Using n = 0 for the first term
    Don't substitute n = 0 thinking it's the starting point = wrong first term! For most sequences, position counting starts at n = 1, not zero. Always use n = 1 for the first term unless specifically told otherwise.

Practice Quiz

Test your knowledge with interactive questions

12 ☐ 10 ☐ 8 7 6 5 4 3 2 1

Which numbers are missing from the sequence so that the sequence has a term-to-term rule?

FAQ

Everything you need to know about this question

Why do we use n = 1 for the first term?

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In most sequences, we start counting positions from 1, not 0. So the first term is at position n = 1, second term at n = 2, and so on. This is the standard convention unless stated otherwise.

What if the sequence started at n = 0?

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If a problem specifically states the sequence starts at n = 0, then use that! But most sequences start at n = 1. Always read the problem carefully for any special instructions.

How can I find other terms in this sequence?

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Just substitute different values of n! For example:

  • Second term: 6(2)1=11 6(2) - 1 = 11
  • Third term: 6(3)1=17 6(3) - 1 = 17
  • Fourth term: 6(4)1=23 6(4) - 1 = 23

What does the formula 6n - 1 tell me about the sequence?

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This formula shows that each term increases by 6 from the previous term. It's an arithmetic sequence with first term 5 and common difference 6.

How do I check if my answer is correct?

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Calculate a few terms to see if they make sense! If your first term is 5, then the second should be 11, third should be 17, etc. Each term should be 6 more than the previous one.

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