Answer
$\color{blue}{f(x)=9x}$
Work Step by Step
RECALL:
The linear function $f(x)=ax+b$ has a slope of $a$ and a y-intercept of $(0, b)$.
The given linear function has a slope of $9$ and a y-intercept of $(0, 0)$.
This means that $a=9$ and $b=0$.
Thus, the equation of the linear function is:
$f(x) = 9x + 0
\\\color{blue}{f(x)=9x}$
