\ \ \ \ \ \ \ \ \
\

Slope of the line

\
\

The slope of a non-vertical line through any two points is given by

\

            \"\"

\
\

\"\"

\

Substitute \"\" in slope formula.

\

\"\" \ \ \"\" (Find the cross products: If \"\" then\"\")

\

\"\"     (Distributive property: \"\")

\

\"\"

\

\"\"           (Multiply: \"\") \ \

\

\"\"                     (Add: \"\") \ \

\

\"\"        (Subtract 9 from each side)

\

\"\"                     (Simplify)

\

\"\"               (Divide each side by -3)

\

\"\"                        (Cancel common terms)

\

\"\"                              (Divide: \"\")

\

\"\"

\

The value of r is \"\".