Algebra II : Summations and Sequences

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #11 : Arithmetic Series

An arithmetic sequence is given by the formula .  What is the difference between  and 

Possible Answers:

Correct answer:

Explanation:

You can either calculate the vaules of  and  and subtract, or notice from the formula that each succesive number in the sequence is 3 larger than the previous

Example Question #13 : How To Find The Nth Term Of An Arithmetic Sequence

Consider the following arithmetic sequence:

What is the term?

Possible Answers:

Correct answer:

Explanation:

A simple way to find the  term of an arithmetic sequence is to use the formula .

Here,  is the term you are trying to find,  is the first term, and  is the common difference. For this question, the common difference is .

 

Example Question #5 : How To Find The Missing Number In A Set

Which number is needed to complete the following sequence:

1,5,_,13,17

Possible Answers:

Correct answer:

Explanation:

This is a sequence that features every other positive, odd integers.  The missing number in this case is 9.  

Example Question #21 : Arithmetic Series

Find the next term in the following arithmetic series:

Possible Answers:

Correct answer:

Explanation:

Find the next term in the following arithmetic series:

To find the next term in an arithmetic series, we need to find the common difference. To do so, find the difference between any two consecutive terms in the sequence:

Our common difference is 7. Now we need to add that to the last term to get what we want

So our next term is 32

 

Example Question #22 : Arithmetic Series

What is the common difference of the following arithmetic series?

Possible Answers:

Correct answer:

Explanation:

What is the common difference of the following arithmetic series?

 

To find the common difference, we need to find the difference between any  two consecutive terms.

Try with the first two:

To be sure, try it with the 2nd and 3rd

We keep getting the same thing, -8. It must be negative, because our sequence is decreasing. Therefore, we have our answer: -8

Example Question #21 : Arithmetic Series

What is the 16th term in the sequence that starts with 7, 4, 1, ...?

Possible Answers:

Correct answer:

Explanation:

The sequence is decreasing by 3 each term. To get from the first term to the 16th term, you must subtract 3 fifteen times:

Example Question #24 : Arithmetic Series

Solve the series:  

Possible Answers:

Correct answer:

Explanation:

Write the n-th term formula.

The  represents the first term, and  is the last term.  

The  is the common difference among the numbers.  

 since each term increases by two.

Solve for .

Divide by two on both sides.

The formula for n-terms in a arithmetic sequence is:

Substitute the known terms.

The answer is:  

Example Question #25 : Arithmetic Series

Determine the sum of:  

Possible Answers:

Correct answer:

Explanation:

Write the formula for the sum of an arithmetic series.

To determine the value of , use the formula:

Divide by five on both sides.

Substitute all the terms into the sum formula.

The answer is:  

Example Question #26 : Arithmetic Series

Determine the sum of:  

Possible Answers:

Correct answer:

Explanation:

Write the formula to determine the sum of an arithmetic series.

where  is the number of terms,  is the first term, and  is the last term.

Use the following formula to determine how many terms are in this series.

The term  is the common difference.  Since the numbers are spaced five units, .

Substitute the known values and solve for n.

Subtract two from both sides, and distribute the five through the binomial.

Add five on both sides.

Divide by five.

Plug this value and the other givens to the sum formula to determine the sum.

The answer is:  

Example Question #27 : Arithmetic Series

If the first term is 4, and the common difference is 3, what is the formula for the sequence?

Possible Answers:

Correct answer:

Explanation:

This represents an arithmetic sequence.  Write the formula.  

Substitute the first term and the common difference in the formula.

Simplify the terms.

The answer is:  

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