Answer :
[tex]\text{Given that,}~~\\\\(x_1, y_1) = (-10,9)~~\text{and}~~ (x_2,y_2) = (-12,7)\\\\\\\text{Slope,}~~ m = \dfrac{y_2 - y_1}{x_2 -x_1}= \dfrac{7-9}{-12+10} =\dfrac{-2}{-2} = 1[/tex]
[tex]\text{Given that,}~~\\\\(x_1, y_1) = (-10,9)~~\text{and}~~ (x_2,y_2) = (-12,7)\\\\\\\text{Slope,}~~ m = \dfrac{y_2 - y_1}{x_2 -x_1}= \dfrac{7-9}{-12+10} =\dfrac{-2}{-2} = 1[/tex]