How do I know when to shade above or below for inequalities?
Answer
Determining whether to shade above or below the line depends on the inequality sign. Lets say if I have greater than or equal to sign in my equation. I would be shading above the line I have graphed. I would do vice versa if it was less than or equal to.
Here are some examples keep in mind of the this formula (y=mx+b)
y<2x+5
2/1 is our slope
5 is our y-int=(0,5)
so we plot our point at our y-int(0,5) and do our rise over run so up 2 to the right 1 to plot our second point. Now since y is less than we would be shaded below and it would be a dotted line as a result.
Lets do another example
Y>or equal to -4x-7
slope is -4/1
y-int is -7=(0,-7)
So we plot our first point at (0,-7) then we do our rise over run so down 4 to the right 1. Since we have a greater than or equal to sign the line is going to be solid and shaded above the line.