ANSWER :
The equation of g(x) is :
[tex]g(x)=\frac{x^2}{9}[/tex]
EXPLANATION :
Note that stretching a function horizontally by a factor of c :
[tex]f(x)\rightarrow f(\frac{x}{c})[/tex]
From the problem, we have a function f(x) = x^2
and g(x) is the graph of f(x) when horizontally stretched by a factor of 3.
Then :
[tex]g(x)=f(\frac{x}{3})[/tex]
Substitute x/3 to the parent function f(x) = x^2 :
[tex]\begin{gathered} g(x)=(\frac{x}{3})^2 \\ g(x)=\frac{x^2}{9} \end{gathered}[/tex]
