If you want it to be y=mx+b form then the equations should look like this: y=x+5 and y=-1/3x+1.
The area of a circle is given by

If you want to approximate pi with 3.14, the formula becomes

If the inequality has < or >, then your graph will have a linear inequality. This is still a line and a half-plane.
Answer: Linear inequality
+ = <3