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

Question

In the drawing, four main structures of the series.

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

Video Solution

Solution Steps

00:00 Find the sequence formula
00:03 Count the circles in each term
00:48 Let's substitute the first term in each equation and see if it works
00:54 Now let's see if the formula works for the second term
01:02 The formula doesn't match the second term, this is not the sequence formula
01:08 Let's continue with the same method to find the correct formula
01:15 Let's check the first term with this formula
01:25 Let's also check the second term
01:32 The formula doesn't match the second term, this is not the sequence formula
01:42 Let's check the first term with this formula
01:53 The formula doesn't match the first term, this is not the sequence formula
01:59 Let's check the first term with this formula
02:06 Let's also check the second term
02:19 And this is the solution to the problem

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) .

Answer

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