Point slope form:
[tex]y-y_1=m(x-x_1) [/tex]
m=slope
(x1,y1)
First we need to find the slope using the slope formula:
[tex] \frac{y_2-y_1}{x_2-x_1} =slope[/tex]
Given the two coordinates:
(1, 9) and (−1, 11)
Plug them into the slope formula:
[tex] \frac{11-9=2}{-1-1=-2} =slope[/tex]
Simplify:
[tex] \frac{2}{-2} =-1[/tex]
Now we know that:
m=-1 and the (x1,y1) would be (1, 9)
Now we simply plug in the info:
[tex]y-9=-(x-1) [/tex]
Final answer: y − 9 = −(x − 1)
