Writing Quadratic Functions and Equations: Mastery Test

The number of guests per month at a large resort is given in the table below, where [tex]$f(x)$[/tex] is the number of guests, in hundreds, [tex]$x$[/tex] months since the beginning of the year.

\begin{tabular}{|c|c|c|c|c|c|c|}
\hline
[tex]$x$[/tex] & 0 & 2 & 4 & 6 & 8 & 10 \\
\hline
[tex]$f(x)$[/tex] & 10 & 15 & 18 & 19 & 18 & 15 \\
\hline
\end{tabular}

Use the data in the table to create the standard form of the function that models this situation, where [tex]$a, b$[/tex], and [tex]$c$[/tex] are constants.

[tex]$f(x) = ax^2 + bx + c$[/tex]



Answer :

To find the quadratic function [tex]\(f(x) = ax^2 + bx + c\)[/tex] that models the given data, we start by identifying the key characteristics of a quadratic function:

1. The quadratic function is represented as [tex]\( f(x) = ax^2 + bx + c \)[/tex].
2. We have the values of [tex]\( x \)[/tex] and [tex]\( f(x) \)[/tex] from the table. Here, [tex]\( x \)[/tex] represents time in months, and [tex]\( f(x) \)[/tex] represents the number of guests (in hundreds).

Given data points:
[tex]\[ \begin{array}{|c|c|c|c|c|c|c|} \hline x & 0 & 2 & 4 & 6 & 8 & 10 \\ \hline f(x) & 10 & 15 & 18 & 19 & 18 & 15 \\ \hline \end{array} \][/tex]

Using these points, we aim to find the quadratic coefficients [tex]\(a\)[/tex], [tex]\(b\)[/tex], and [tex]\(c\)[/tex]. After analysis, we find that the quadratic equation which fits these points is:

[tex]\[ f(x) = -0.25x^2 + 3x + 10 \][/tex]

Here’s the breakdown of the identified coefficients:
- The coefficient [tex]\(a\)[/tex] (the quadratic term coefficient) is [tex]\(-0.25\)[/tex].
- The coefficient [tex]\(b\)[/tex] (the linear term coefficient) is [tex]\(3.0000000000000004\)[/tex]. For practical purposes and in context, this can be approximated to [tex]\(3\)[/tex].
- The coefficient [tex]\(c\)[/tex] (the constant term) is [tex]\(10\)[/tex].

Thus, the quadratic function that models the number of guests per month at the resort is:

[tex]\[ f(x) = -0.25x^2 + 3x + 10 \][/tex]