\begin{tabular}{|c|c|}
\hline
[tex]$x$[/tex] & [tex]$f(x)$[/tex] \\
\hline
-3 & 18 \\
\hline
-2 & 3 \\
\hline
-1 & 0 \\
\hline
0 & 3 \\
\hline
1 & 6 \\
\hline
2 & 3 \\
\hline
\end{tabular}

Using only the values given in the table for the function [tex]$f(x)=-x^3+4x+3$[/tex], what is the largest interval of [tex]$x$[/tex] values where the function is increasing?

[tex]$\square$[/tex]
[tex]$\square$[/tex]



Answer :

To determine the interval where the function is increasing, we need to examine the given table of values for the function [tex]\( f(x) \)[/tex]:

[tex]\[ \begin{array}{|c|c|} \hline x & f(x) \\ \hline -3 & 18 \\ \hline -2 & 3 \\ \hline -1 & 0 \\ \hline 0 & 3 \\ \hline 1 & 6 \\ \hline 2 & 3 \\ \hline \end{array} \][/tex]

First, let's list the points and observe the changes in the function values as [tex]\( x \)[/tex] increases:

- From [tex]\( x = -3 \)[/tex] to [tex]\( x = -2 \)[/tex], [tex]\( f(x) \)[/tex] decreases from 18 to 3.
- From [tex]\( x = -2 \)[/tex] to [tex]\( x = -1 \)[/tex], [tex]\( f(x) \)[/tex] decreases from 3 to 0.
- From [tex]\( x = -1 \)[/tex] to [tex]\( x = 0 \)[/tex], [tex]\( f(x) \)[/tex] increases from 0 to 3.
- From [tex]\( x = 0 \)[/tex] to [tex]\( x = 1 \)[/tex], [tex]\( f(x) \)[/tex] increases from 3 to 6.
- From [tex]\( x = 1 \)[/tex] to [tex]\( x = 2 \)[/tex], [tex]\( f(x) \)[/tex] decreases from 6 to 3.

Next, we identify the intervals where [tex]\( f(x) \)[/tex] is increasing. From the observations above:

- [tex]\( f(x) \)[/tex] is increasing from [tex]\( x = -1 \)[/tex] to [tex]\( x = 0 \)[/tex].
- [tex]\( f(x) \)[/tex] is increasing from [tex]\( x = 0 \)[/tex] to [tex]\( x = 1 \)[/tex].

Thus, the intervals where [tex]\( f(x) \)[/tex] is increasing are [tex]\((-1, 0)\)[/tex] and [tex]\((0, 1)\)[/tex].

Since these two intervals are adjacent and can be combined into a single continuous interval, the largest interval where the function is increasing is:

[tex]\[ (-1, 1) \][/tex]

Therefore, the largest interval of [tex]\( x \)[/tex] values where the function is increasing is [tex]\((-1, 1)\)[/tex].