# find if point lies in given graph

i have following question and please help me,suppose that we have region on coordinante systems bounded by lines $x=0$,$=0$,$y=1-x$ we have to enter some point let's sat M,with x,y coordinates,my aim is to show if given point lies on this bounded interval,just one thing which i didn't understand is that,should i use theorem of right triangle or what?i need a little explanation ,for example i want to write program and want to understand correctly mathematical definition of this problem

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Have you made a drawing of your region? You should be able to construct appropriate inequalities from that. – J. M. Feb 9 '12 at 11:09
You're missing something in the second equation. Also, do they have periods where you come from, or only commas? – Gerry Myerson Feb 9 '12 at 11:13
only commas,graph of this interval is just right triangle – dato datuashvili Feb 9 '12 at 11:30

Now, take your first line equation $x = 0$ that's just the $x$-axis. Looking at the picture, the region you want extends to the right along this axis, so you set $x \geq 0$. The second equation is (I assume) $y = 0$. Looking at the picture, the region you want extends to the top, along this axis, so you set $y \geq 0$. Finally, the last boundary is $y = 1-x$. Looking the the picture, you want the points to be under that line, so you set $y \leq 1-x$.
You're done, a point with coordinates $(a,b)$ will be in the triangle iff $a, b$ are both non-negative, and $b \leq 1-a$.