Find the Algebraic Expression: Converting Point Patterns to nth Term Formula

In the drawing, four main structures of the series.

Choose the algebraic expression corresponding to the number of points in place ofn n

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:06 Let's find the formula for this sequence.
00:09 Count how many circles are in each term.
00:54 Now, substitute the first term into the equation to see if it works.
01:00 Let's check if the formula applies to the second term.
01:08 This formula doesn't match the second term, so it's not correct.
01:14 Keep going! Use the same method to find the right formula.
01:21 Check if the first term fits this new formula.
01:31 Let's see if it also works with the second term.
01:38 Oops! This formula doesn't fit the second term.
01:48 Test the first term again with a different formula.
01:59 The first term doesn't match. Let's try another formula.
02:05 Test the first term with this formula.
02:12 Check it with the second term as well.
02:25 Great job! That's how we solve the problem.

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

In the drawing, four main structures of the series.

Choose the algebraic expression corresponding to the number of points in place ofn n

2

Step-by-step solution

The aim is to find a formula for the number of points (or dots) in structure based on the input n n . Let's consider the visible pattern in the structures:

By considering four instances, we deduce:

  • For n=0 n=0 : The structure has 2 points.
  • For n=1 n=1 : The structure has 4 points.
  • For n=2 n=2 : The structure has 6 points.
  • For n=3 n=3 : The structure has 8 points.

Observing closely, each subsequent structure increases by 2 points consistently.

Now, we try to formulate this pattern algebraically:

The number of points seems directly proportional to n n , leading to the formula 2(n+1) 2(n + 1) , where each increase in n n results in 2 additional points.

Verify:

  • For n=0 n=0 , 2(0+1)=2 2(0 + 1) = 2 .
  • For n=1 n=1 , 2(1+1)=4 2(1 + 1) = 4 .
  • For n=2 n=2 , 2(2+1)=6 2(2 + 1) = 6 .
  • For n=3 n=3 , 2(3+1)=8 2(3 + 1) = 8 .

The pattern and derived expression 2(n+1) 2(n + 1) consistently apply.

Thus, the answer is 2(n+1) \boxed{2(n + 1)} .

From the choices provided, the correct algebraic expression for the number of points in place of n n corresponds directly to choice 2: 2(n+1) 2(n + 1) .

3

Final Answer

2(n+1) 2(n+1)

Practice Quiz

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Is there a term-to-term rule for the sequence below?

18 , 22 , 26 , 30

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