Graph the feasible region for the system of inequalities calculator

Video transcript

We're asked to determine the solution set of this system, and we actually have three inequalities right here. A good place to start is just to graph the solution sets for each of these inequalities and then see where they overlap. And that's the region of the x, y coordinate plane that will satisfy all of them. So let's first graph y is equal to 2x plus 1, and that includes this line, and then it's all the points greater than that as well. So the y-intercept right here is 1. If x is 0, y is 1, and the slope is 2. If we move forward in the x-direction 1, we move up 2. If we move forward 2, we'll move up 4, just like that. So this graph is going to look something like this. Let me graph a couple more points here just so that I make sure that I'm drawing it reasonably accurately. So it would look something like this. That's the graph of y is equal to 2x plus 1. Now, for y is greater than or equal, or if it's equal or greater than, so we have to put all the region above this. For any x, 2x plus 1 will be right on the line, but all the y's greater than that are also valid. So the solution set of that first equation is all of this area up here, all of the area above the line, including the line, because it's greater than or equal to. So that's the first inequality right there. Now let's do the second inequality. The second inequality is y is less than 2x minus 5. So if we were to graph 2x minus 5, and something already might jump out at you that these two are parallel to each other. They have the same slope. So 2x minus 5, the y-intercept is negative 5. x is 0, y is negative 1, negative 2, negative 3, negative 4, negative 5. Slope is 2 again. And this is only less than, strictly less than, so we're not going to actually include the line. The slope is 2, so it will look something like that. It has the exact same slope as this other line. So I could draw a bit of a dotted line here if you like, and we're not going to include the dotted line because we're strictly less than. So the solution set for this second inequality is going to be all of the area below the line. For any x, this is 2x minus 5, and we care about the y's that are less than that. So let me shade that in. So before we even get to this last inequality, in order for there to be something that satisfies both of these inequalities, it has to be in both of their solution sets. But as you can see, their solutions sets are completely non-overlapping. There's no point on the x, y plane that is in both of these solution sets. They're separated by this kind of no-man's land between these two parallel lines. So there is actually no solution set. It's actually the null set. There's the empty set. Maybe we could put an empty set like that, two brackets with nothing in it. There's no solution set or the solution set of the system is empty. We could do the x is greater than 1. This is x is equal to 1, so we put a dotted line there because we don't want include that. So it would be all of this stuff. But once again, there's nothing that satisfies all three of these. This area right here satisfies the bottom two. This area up here satisfies the last one and the first one. But there's nothing that satisfies both these top two. Empty set.

Instructor: Elizabeth Foster Show bio

Elizabeth has been involved with tutoring since high school and has a B.A. in Classics.

The feasible region of a system of inequalities is graphed by including all inequalities located within the system. Learn about the feasible region, how to graph a system of inequalities, and learn how to test the feasible region. Updated: 11/23/2021

The Feasible Region. It sounds like the title of a futuristic spy flick where everything is green and black and everyone wears sci-fi clothing with no pockets. In a world where global warming has left most of the Earth uninhabitable, a corrupt dictatorship controls the Feasible Region, the only place left that can support life… or is it?

But as fun as that movie might be to watch, in math, the feasible region is actually something else. The feasible region of a system of inequalities is the area of the graph showing all the possible points that satisfy all inequalities.

OK, it's not as dramatic, even if you also put in a green-and-black futuristic color scheme. But knowing how to find the feasible region of a system of inequalities is really useful, so in this lesson we'll walk through how to do it.

• Video
• Quiz
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Graphing a System of Inequalities

To start, let's review how to graph one inequality. First, replace the inequality sign with an equals sign and graph the line. Then shade the region above or below the line, depending on which values satisfy the original inequality.

Here's a quick example. Let's say we want to graph y > x . First, we'll replace the inequality sign with an equals sign and graph the line y = x .

On one side of this line will be all the points where y is less than x, and on the other side will be all the points where y is greater than x. We just need to figure out which side is which so we'll plug in a test point from each side.

We can see that below the line, y < x and above the line, y > x. So to graph the inequality y > x, we'll shade the area above the line. It's a little bit hard to see, but we'll also make the original line a dashed line, to show that y = x is technically not part of the solution.

When you graph a system of inequalities, you're basically doing that exact same process for several lines on the same graph. So instead of graphing just the points that fit y > x, you might want to graph the points that fit all of the following:

• y > x
• x > -5
• y < 6

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How do you graph the feasible region for the system of inequalities?

What is the feasible region for a system of inequalities?