Question 204437
They way I do these is plot the line {{{x + y =1}}}
Then shade in the area "less than" that line (below it)

See this site for doing plots like this --> http://www91.wolframalpha.com/input/?i=x+%2B+y+%3C+1+

Also, you can download geogebra and use that tool too (geogebra.org)