Seats in a theater are curved from the front row to the back. The front row has 10 chairs, the second has 16 and the third has 22, and so on. A. Write a recursive rule for this series

B. Write an explicit rule for this series

C. Using the explicit formula, find the number of chairs in row 5

D. The auditorium can hold 17 rows of chairs. Write a sigma notation for this series, and then use either series formula to calculate how many chairs can fit in the auditorium

The first term is 10.

The second term is 16

The third term is 22.

We can see that the first term plus 6, is:

10 + 6 = 16

Then the first term plus 6 is equal to the second term.

And the second term plus 6 is:

16 + 6 = 22

Then the second term plus 6 is equal to the third term.

A) As we already found, the recursive rule is:

Aₙ = Aₙ₋₁ + 6

B) The explicit rule is:

Aₙ = A₁ + (n - 1)*6

Such that A1 is the first term, in this case A₁ = 10

Then:

Aₙ = 10 + (n - 1)*6

C)

Now we want to find A₅, then:

A₅ = 10 + (5 - 1)*6 = 34

There are 34 chairs in row 5.

D)

Here we have 17 rows, then we can have 17 terms, this means that the total number of chairs will be:

C = A₀ + A₁ + ... + A₁₆

This summation can be written as:

∑ 10 + (n - 1)*6        such that n goes from 0 to 16.

The formula  for the sum of the first N terms of a sum like this is:

S(N) = (N)*(A₁ + Aₙ)/2

Then the sum of the 17 rows gives:

S(17) = 17*(10 + (10 + (17 - 1)*6)/2 = 986 chairs.