Points on the graph = (0,1) and (1,0)
Slope of line = [ 0 -1 ] / [ 1 - 0 ] = -1 / 1 = -1
Equation of line y = -x + 1 → x + y = 1
Equation of inequality is either
x + y ≥ 1
or
x + y ≤ 1
(1,1) is in the solution area and makes the first inequality true