I'm not sure what "point slope" form is.
I'll give the form slope intercept.
y = ax+b
a is the slope, b is the y-intercept.
As we can see, the slope is (rise over run), and since the coordinates, (2,-1), and if you go up the next point on a grid is (1,1). Rise, 2, run, -1.
Slope is thus -2.
y = -2x + b.
At a increase of slope 2, so for every 1 it goes left, it goes up 2.
We need to go left twice, so 2x2 = 4.
-1 + 4 = 3/
Thus the equation is
y = -2x + 3