Answer: A. 9
Step-by-step explanation:
Given: The red line and the green line are perpendicular to each other.
The slope of green line =\(\dfrac{-1}{9}\)
We know that the product of slopes of two perpendicular line is -1.
Let m be the slope of red line ], then we have
\(\dfrac{-1}{9}\times m=-1\\\\\Rightarrow\ m=\dfrac{9}{1}=9\)
Hence, the slope of the red line = 9.
