The transformation of function and their algebraic representation are shown below:
From it we notice that to reflect the function about the y-axis we need to change the sign of the variable, then we have:
[tex]\begin{gathered} g(x)=9(-x) \\ g(x)=-9x \end{gathered}[/tex]
Therefore, the expression of g is:
[tex]g(x)=-9x[/tex]
