Question

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Answer 1

The chairs in the auditorium illustrates an arithmetic sequence

• The recursive rule is:  an = an-1 + 8; a1 = 26
• The explicit rule is:  an = 18 + 8n
• There are 74 seats in the 7th row
• 840 chairs can fit the auditorium

The recursive rule

From the question, we have the following sequence:

Seats: 18, 26, 34

Rewrite as:

26 = 18 + 8

34 = 26 + 8

The above means that:

The number of seats on a row is 8 added to the the number of seats on the previous row.

Hence, the recursive rule is:

an = an-1 + 8; a1 = 26

The explicit rule

In (a), we have:

a1 = 26 and d = 8

The explicit rule is calculated using:

an = a1 + (n -1) * d

This gives

an = 26 + (n - 1) * 8

Expand

an = 26 - 8 + 8n

Evaluate the difference

an = 18 + 8n

Hence, the explicit rule is:

an = 18 + 8n

The number of seats in the row 7

This means that n = 7.

So, we  have:

a7 = 18 + 8 * 7 = 74

Hence, there are 74 seats in the 7th row

The sigma notation

We have the maximum number of rows to be 12.

So, the sigma notation would be:

$\sum\limits^{12}_{n=1} {18 + 8n}$

The total number of seats is:

Sn = n/2(2a + (n -1) * d)

This gives

S12 = 12/2(2 * 26 + (12 -1) * 8)

S12 = 840

Hence, 840 chairs can fit the auditorium

Read more about arithmetic sequence at:

brainly.com/question/6561461