High School

The profit function for a business is given by the equation [tex]P(x) = -4x^2 + 16x - 7[/tex], where [tex]x[/tex] is the number of items sold, in thousands, and [tex]P(x)[/tex] is the profit in dollars, in thousands.

Calculate the maximum profit.

A. [tex]$9000[/tex]
B. [tex]$29000[/tex]
C. [tex]$11000[/tex]
D. [tex]$7000[/tex]

Answer :

To find the maximum profit for the given profit function, we have the equation [tex]\( P(x) = -4x^2 + 16x - 7 \)[/tex]. This equation is a quadratic in the standard form [tex]\( ax^2 + bx + c \)[/tex].

Since this is a quadratic function, its graph is a parabola. Because the coefficient of [tex]\( x^2 \)[/tex] is negative ([tex]\( -4 \)[/tex]), the parabola opens downward, which means it has a maximum point at the vertex.

To find the x-coordinate of the vertex for a parabola described by the equation [tex]\( ax^2 + bx + c \)[/tex], we use the formula:

[tex]\[ x = -\frac{b}{2a} \][/tex]

Let's apply this formula:

- [tex]\( a = -4 \)[/tex]
- [tex]\( b = 16 \)[/tex]

Plug these values into the vertex formula:

[tex]\[ x = -\frac{16}{2 \times -4} \][/tex]
[tex]\[ x = -\frac{16}{-8} \][/tex]
[tex]\[ x = 2 \][/tex]

The x-coordinate of the vertex is [tex]\( x = 2 \)[/tex], which corresponds to 2,000 items since [tex]\( x \)[/tex] is in thousands.

Next, we calculate the maximum profit by substituting this x-coordinate back into the profit function [tex]\( P(x) \)[/tex]:

[tex]\[ P(2) = -4(2)^2 + 16(2) - 7 \][/tex]
[tex]\[ P(2) = -4 \times 4 + 16 \times 2 - 7 \][/tex]
[tex]\[ P(2) = -16 + 32 - 7 \][/tex]
[tex]\[ P(2) = 16 - 7 \][/tex]
[tex]\[ P(2) = 9 \][/tex]

Hence, the maximum profit is [tex]\( 9 \)[/tex] thousand dollars, which means [tex]$9,000.

Therefore, the maximum profit is $[/tex]\[tex]$9,000$[/tex].