Answer: -1/9
Explanation: Perpendicular lines have negative reciprocal slopes.
A negative reciprocal slope is a fancy way of
saying flip the fraction and change the sign.
Notice that our slope is an integer.
We can turn it into a fraction by putting it over 1.
So we have 9/1.
A line perpendicular to this would be a negative reciprocal.
So flip the fraction, giving us 1/9, and change the sign to get -1/9.
