Question

algebra
review passage
the revenue (r) from the number of sales (x) of a certain videogame is described by the function:
r(x) = -0.14x² + 420x
question
what is the maximum revenue?
select a single answer
1,500
315,000
31,500
15,000
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Explanation:

Step1: Find vertex x-coordinate

For quadratic $R(x)=ax^2+bx+c$, $x=-\frac{b}{2a}$
Here $a=-0.14$, $b=420$:
$x=-\frac{420}{2\times(-0.14)}=\frac{420}{0.28}=1500$

Step2: Compute max revenue

Substitute $x=1500$ into $R(x)$:
$R(1500)=-0.14(1500)^2+420(1500)$
$=-0.14\times2,250,000 + 630,000$
$=-315,000 + 630,000=315,000$

Answer:

315,000