Find the 7th Term in Sequence: 2(2n-2) Step-by-Step

Sequence Terms with Substitution Method

Below is the rule for a sequence in terms of n n :

2(2n2) 2(2n-2)

What is the value of the 7th element 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 7th element
00:04 Location of the desired element according to the data
00:11 Substitute appropriate values according to the data and solve to find the element
00:23 Always solve parentheses first
00:27 Always solve multiplication and division before addition and subtraction
00:38 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Below is the rule for a sequence in terms of n n :

2(2n2) 2(2n-2)

What is the value of the 7th element in the sequence?

2

Step-by-step solution

To determine the 7th element of the sequence defined by the rule 2(2n2)2(2n - 2), we follow these steps:

  • Step 1: Identify the given formula for the sequence, which is 2(2n2)2(2n - 2).

  • Step 2: Simplify this formula to its basic form. By expanding, we have: 2×(2n2)=4n4.2 \times (2n - 2) = 4n - 4.

  • Step 3: Substitute n=7n = 7 into the simplified formula 4n44n - 4.

  • Step 4: Perform the calculation:
    4n4=4×74=284=24 \begin{aligned} 4n - 4 &= 4 \times 7 - 4 \\ &= 28 - 4 \\ &= 24 \end{aligned}

Thus, the 7th element of the sequence is 24\boldsymbol{24}.

3

Final Answer

24 24

Key Points to Remember

Essential concepts to master this topic
  • Formula: Use given rule 2(2n2) 2(2n-2) and substitute position value
  • Technique: Simplify first: 2(2n2)=4n4 2(2n-2) = 4n-4 , then substitute n=7 n=7
  • Check: Verify calculation: 4(7)4=284=24 4(7)-4 = 28-4 = 24

Common Mistakes

Avoid these frequent errors
  • Substituting n = 7 into the original formula without simplifying
    Don't calculate 2(2×7-2) = 2(14-2) = 2(12) = 24 directly without simplifying! While this gives the correct answer, it's harder and more error-prone with complex formulas. Always simplify the formula first to 4n-4, then substitute n = 7.

Practice Quiz

Test your knowledge with interactive questions

Look at the following set of numbers and determine if there is any property, if so, what is it?

\( 94,96,98,100,102,104 \)

FAQ

Everything you need to know about this question

Do I always need to simplify the formula before substituting?

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While not strictly required, simplifying first makes calculations easier and reduces errors. Compare 2(2n2) 2(2n-2) versus 4n4 4n-4 - the simplified version is much cleaner!

What does n represent in sequence formulas?

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n represents the position number of the term you want to find. For the 7th term, n = 7. For the 1st term, n = 1. It's like the "address" of each term in the sequence.

How do I know if I substituted correctly?

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Double-check by asking: "Did I replace every n with 7?" In 4n4 4n-4 , there's only one n, so it becomes 4(7)4 4(7)-4 .

What if I get a negative answer?

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Negative sequence terms are perfectly valid! Just follow the same steps: substitute the position number and calculate carefully, keeping track of positive and negative signs.

Can I check my answer another way?

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Yes! Calculate a few nearby terms like the 6th and 8th terms. If your sequence is 4n4 4n-4 , the 6th term is 20 and 8th term is 28, so 24 for the 7th term makes sense!

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