That's made of two functions

y = 2x+1 and y = -x-1

The cut off number is 0.

Pick two values of x greater than the cut-off number 0 
and substitute them into

y = 2x+1

 x |  y
 1 |  3
 2 |  5

Plot those two points and draw a line through them only to the 
RIGHT of the cut off point:

Pick two values of x less than the cut-off number 0 
and substitute them into

y = -x-1

 x |  y
-2 |  1
-3 |  2

Plot those two points and draw a line through them only to the 
LEFT of the cut off point 0.

Put an open circle at the end of the one that does not include 
0 and a closed circle at the end of the one that does include 0.



 
Edwin