Is 8 a Term of the Quadratic Sequence 2n²?

Quadratic Sequences with Term Verification


2n2 2n^2

Is the number 8 a term in the sequence above?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Is the number 8 a member of the sequence?
00:03 Let's substitute the term in the sequence formula and solve for N
00:08 If the solution for N is positive and whole, then this is the position of the term
00:11 Let's isolate N
00:23 When taking a root there are always 2 solutions, positive and negative
00:29 N must be positive, therefore this solution is not relevant
00:35 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


2n2 2n^2

Is the number 8 a term in the sequence above?

2

Step-by-step solution

To solve this problem, we'll perform the following steps:

  • Step 1: Set up the equation 2n2=8 2n^2 = 8 .
  • Step 2: Simplify the equation by dividing both sides by 2, resulting in n2=4 n^2 = 4 .
  • Step 3: Solve for n n by taking the square root of both sides, leading to n=±2 n = \pm 2 .
  • Step 4: Since sequence indices are positive integers, consider n=2 n = 2 .

Now, let's see if 8 is a term in the sequence:
Starting with the equation 2n2=8 2n^2 = 8 :

2n2=8 2n^2 = 8

Step 2: Divide both sides by 2:

n2=4 n^2 = 4

Step 3: Take the square root of both sides:

n=±2 n = \pm 2

Since n n must be a positive integer for this sequence, we choose n=2 n = 2 .

This confirms that 8 can be expressed as 2(22)=8 2(2^2) = 8 . Thus, 8 is a term in the sequence.

Therefore, the solution to the problem is Yes.

3

Final Answer

Yes.

Key Points to Remember

Essential concepts to master this topic
  • Setup: Set equation 2n2=8 2n^2 = 8 to find term position
  • Solve: Divide by 2 to get n2=4 n^2 = 4 , then n=2 n = 2
  • Verify: Check 2(2)2=2(4)=8 2(2)^2 = 2(4) = 8

Common Mistakes

Avoid these frequent errors
  • Accepting negative values for sequence position
    Don't use n=2 n = -2 from n=±2 n = ±2 = invalid position! Sequence positions must be positive integers since you can't have a negative term number. Always use only positive integer solutions for sequence positions.

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

Why can't I use n = -2 as a valid solution?

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In sequences, n represents the position of a term (1st, 2nd, 3rd, etc.). Since you can't have a negative position like "-2nd term," only positive integer values of n make sense for sequences.

What if the equation has no positive integer solutions?

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Then the number is not a term in the sequence! For example, if solving 2n2=7 2n^2 = 7 gives non-integer values, then 7 isn't in the sequence.

Do I always need to solve a quadratic equation for these problems?

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Yes, when checking if a number is in a quadratic sequence like 2n2 2n^2 . You set the sequence formula equal to your target number and solve for n.

How do I verify my answer is correct?

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Substitute your n-value back into the original sequence formula. If 2n2 2n^2 equals your target number, then yes, it's a term!

What if I get a decimal value for n?

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If n is not a positive integer, then your target number is not a term in the sequence. Sequence positions must be whole numbers like 1, 2, 3, etc.

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