when graphing, how do I know when to shade and when not to shade. my teacher told me to look at the signs but i still dont understand

Question

psymon · Answer

Well, lets just pick something simple like x + y >= 2 
You had when you can pick an x and a y value that makes the expression true. So if I were to draw that graph I would have this:

|dw:1380833930255:dw|

So lets just say I pick x = 0, y = -2. If I plug those into the equation I have
0 - 2 >= 2

Well, -2 is not >= 2, so I cant shade any area that contains the point (0,-2). But if I pick x = 1 and y = 3. I can plug those values into the equation and get:

1 + 3 >= 2
4 >= 2

Well of course 4 is greater than 2. That means I can shade the whole region that has the point (1,3)

Basically youre checking coordinate points and seeing if they make the equation true:

|dw:1380834108443:dw|