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
00:03 Let's find out if the number 8 belongs to our sequence.
00:07 First, substitute 8 into our sequence formula, and solve for N.
00:12 If N comes out as a positive whole number, then 8 is a part of the sequence.
00:17 Let's work on isolating the variable N.
00:26 Remember, taking a root gives us two solutions: positive, and negative.
00:32 Since N must be positive, we'll focus only on the positive solution.
00:38 And that's how we solve the problem, determining if 8 is in the sequence.

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

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

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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