The point-slope form:
[tex]y-y_1=m(x-x_1)[/tex]
m - slope
The formula of a slope:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
We have the points (-10, -20) ans (1, -9). Substitute:
[tex]m=\dfrac{-9-(-20)}{1-(-10)}=\dfrac{-9+20}{1+10}=\dfrac{11}{11}=1[/tex]
For the first point (-10, -20):
[tex]y-(-20)=1(x-(-10))\\\\\boxed{y+20=1(x+10)}[/tex]
