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The total number of seats in an auditorium is modeled by f(x) = 2x2 - 24x where x represents the number of seats in each row. How many seats are there in each row of the auditorium if it has a total of 1280 seats?
A)32
B)108
C)20
D)640

User Dandrews
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1 Answer

3 votes

Answer:

A) 32

Explanation:

f(x) = 2x² - 24x

If f(x) = 1280, then 2x² - 24x = 1280

Subtract 1280 from both side ⇒ 2x² - 24x - 1280 = 0

Divide both sides by 2 ⇒ x² - 12x - 640 = 0

Factorise ⇒ (x - 32)(x + 20) = 0

Solve ⇒ x = 32 or -20

Therefore, x = 32 (as x ≥ 0)