graphing systems of linear inequalities

bryanandrew

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Feb 1, 2008
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i need help on a problem that deals with this subject. I need to find 2 coordinates that make a line with the first equation and then i need to find another 2 coordinates with the second equation. the only thing is i need to have the second line intersect with the first line on the graph. can ypu help me :?: please :mrgreen:
 

jwpaine

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If you have a linear equation (in slope intercept form) of the form y = mx+b, take any value x and substitute it in, to get your value for y. That will give you one ordered pair (x,y) for every value x. Example: the line y = (1/2)x + 2, for x = 2, y = (1/2)2 + 2 = 1 + 2 = 3, so you have a point (2,3)

John
 

bryanandrew

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Feb 1, 2008
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thank you very much :!: :mrgreen: but that type of method i used was at least 3 to 4 lessons ago, so the way my class does it that we list the coordinates and not solve the equation: Do you know how to do this??? Please
 

Subhotosh Khan

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bryanandrew said:
i need help on a problem that deals with this subject. I need to find 2 coordinates that make a line with the first equation and then i need to find another 2 coordinates with the second equation. the only thing is i need to have the second line intersect with the first line on the graph. can ypu help me :?: please :mrgreen:
What are those equations?

Please put up a complete problem with exact wording - with your work/thoughts and indicate exactly where you are stuck - so that we know where to begin to help you.
 

bryanandrew

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Feb 1, 2008
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the equation has two parts to it. I've figured out the second part but need help on the first part. The equation is: y>4 (1st part)
2y+x>5 (2nd part)
with these equations what I need to do is list the missing numbers (x,y) that best fits the equation. Once I've done that, I put it on a graph, in order for the problem to be correct, the two lines need to intersect. Can you help me?
 

stapel

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bryanandrew said:
the equation has two parts to it.
I think you mean that "the system contains two inequalities"...? "Equations" have an "equals" sign, rather than an inequality symbol.

bryanandrew said:
I've figured out the second part but need help on the first part....
what I need to do is list the missing numbers (x,y) that best fits the equation.
I'm sorry, but I can't figure out what this might mean...? You've already received instruction on how to graph the lines, but you seem to have said that, since you already learned that method a few lectures ago, you cannot, for some reason, now use that method...? What method are you supposed to be using?

Note: Since the solution to a linear inequality of the type you've listed is half of the plane, there are infinitely-many points that "fit" the inequalitiy. To my knowledge, no one point is "better" than another, so there is no "best" point to "fit" the inequality. It might help if you explained what you mean by this...?

Thank you! :D

Eliz.
 
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