The standard form of a line: [tex]Ax+By=C[/tex].
The point-slope form: [tex]y-y_1=m(x-x_1)[/tex]
We have the point (3, -1) and the slope m = -1. Substitute:
[tex]y-(-1)=-1(x-3)[/tex]
[tex]y+1=-x+3[/tex] add x to both sides
[tex]x+y+1=3[/tex] subtract 1 from both sides
[tex]\boxed{x+y=2}[/tex]
