# What is the slope of the line perpendicular to  y=9x +3 ?

I found: $- \frac{1}{9}$
Your line is in the Slope-Intercept form : $y = m x + c$
where $m = 9$ is the slope.
The line perpendicular will have slope $m ' = - \frac{1}{m} = - \frac{1}{9}$