find if the slope of the line through and is the negative of the slope of the
line through and
I know that these slopes do not have to be perpendicular to each other.
Let be the slope of the first line, and be the slope of the second line ..
Since the slope of the first line is the negative of the slope of the second line, we conclude that :
..... (1)
... (2)
... (3)
If we substitute (2) & (3) in (1), we will get the following equation :
Solve the last equation for .