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3 years ago

12

I've tried to get the answer for this 13 times now (not joking), plzzz help: write a formula that represents the number of peopl

e in the nth row (pre-calc problem, I only need the formula)
I will report if sent a link

1 answer:

gtnhenbr [62]3 years ago

6 0

Answer:

2820 seats
aₙ = 3n + 9

Step-by-step explanation:

<u>This is an AP with:</u>

The first term a₁ = 12
Common difference d = 3
Number of terms n = 40

<u>Number of the seats:</u>

Sₙ = 1/2*n(a₁ + aₙ) = 1/2n(2a₁ + (n - 1)d)
S₄₀ = 1/2*40(12*2 + 39*3) = 2820 seats

<u>Formula of nth term:</u>

aₙ = a₁ + (n - 1)d
aₙ = 12 + (n - 1)*3 = 12 + 3n - 3 = 3n + 9
aₙ = 3n + 9

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