Answer:
[tex]y=\dfrac{7}{3}\left(\dfrac{1}{3}\right)^x[/tex]
Step-by-step explanation:
Given table:
[tex]\begin{array}{|c|c|}\cline{1-2} \phantom{\dfrac{1}{1}} x & y \\\cline{1-2} \phantom{\dfrac{1}{1}} -1 & 7 \\\cline{1-2} \phantom{\dfrac{1}{1}} 0 & \frac{7}{3}\\\cline{1-2} \phantom{\dfrac{1}{1}} 1 & \frac{7}{9}\\\cline{1-2} \phantom{\dfrac{1}{1}} 2 & \frac{7}{27}\\\cline{1-2} \phantom{\dfrac{1}{1}} 3 & \frac{7}{81}\\\cline{1-2}\end{array}[/tex]
- Linear function: As x increases by one, y always increases by a constant value. Therefore, the first differences between y-values are the same.
- Quadratic function: The second differences between y-values are the same.
- Exponential function: The y-value either increases or decreases by a constant factor.
Work out the first differences between the y-values:
[tex]7 \underset{-\frac{14}{3}}{\longrightarrow} \dfrac{7}{3} \underset{-\frac{14}{9}}{\longrightarrow} \dfrac{7}{9} \underset{-\frac{14}{27}}{\longrightarrow} \dfrac{7}{27} \underset{-\frac{14}{81}}{\longrightarrow} \dfrac{7}{81}[/tex]
As the first differences are not the same, it is not a linear function.
Work out the second differences:
[tex]-\dfrac{14}{3} \underset{+\frac{28}{9}}{\longrightarrow} -\dfrac{14}{9} \underset{+\frac{28}{27}}{\longrightarrow} -\dfrac{14}{27} \underset{+\frac{28}{81}}{\longrightarrow} -\dfrac{14}{81}[/tex]
As the second differences are not the same, it is not a quadratic function.
Work out if the second differences have a common ratio:
[tex]\implies \sf \dfrac{28}{27} \div \dfrac{28}{9}=\dfrac{1}{3}[/tex]
[tex]\implies \sf \dfrac{28}{81} \div \dfrac{28}{27}=\dfrac{1}{3}[/tex]
As the second differences have a common ratio of ¹/₃, the function is exponential with base ¹/₃.
General form of an exponential function:
[tex]y=a(b)^x[/tex]
where:
- a is the y-intercept.
- b is the base (growth/decay factor) in decimal form.
The y-intercept is the value of y when x = 0.
From inspection of the table, the y-intercept is ⁷/₃.
Therefore:
[tex]a = \dfrac{7}{3}[/tex]
[tex]b = \dfrac{1}{3}[/tex]
Substitute the found values of a and b into the formula to create an exponential function that models the given data:
[tex]\implies y=\dfrac{7}{3}\left(\dfrac{1}{3}\right)^x[/tex]
Learn more about exponential functions here:
https://brainly.com/question/28263307
