The formula to find slope with 2 coordinates is [tex] \frac{ y_{2}- y_{1} }{ x_{2}- x_{1} } [/tex].
Now plug in the variables.
[tex] \frac{-4-9}{u-6} = \frac{13}{9} [/tex]
[tex]-4-9=-13[/tex]
[tex]u-6=-9[/tex]
We must solve for u by adding 6 on both sides of the equation, giving us -3. So, u is -3.
Remember when we do slope, if both the numerator and denominator are negative numbers, it is the same as if they were positive. That is why the both equations resulted into negative number instead of positive numbers.
