What is the slope of a line perpendicular to the line in this graph?

Question

anonymous · Answer

attachment

radar · Answer

I would look closely and find two easily located points.
After very careful perusal I have selected point P1 as......well the print on your drawing is so small, these 74 year old eyes can't discern their value.  Assuming each interval is 1, P1 is (0, 1) and P2 is (3, -3)  Do you see the locations that I am trying to read?

radar · Answer

OK, I have zoomed the drawing and those points have the same value as I have shown.
Now here is the  plan:
First find the slope of the line in your drawing.
Second.  find the slope in the line that would be perpendicular.
Does that sound like a plan?

radar · Answer

This is not going to be a monologue!