Respuesta :

r=-9.

you can use the formula for slope to find the answer.
[tex]slope = \frac{y_2-y_1}{x_2-x_1} \\ -1= \frac{r--6}{9-6} = \frac{r+6}{3} \\ -1=\frac{r+6}{3} \\ -3=r+6 \\ r=-9[/tex]

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