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Question 169654: Photobucket
my question is :

a student graphed a system of inequalities, shading only the region containong the solutions of the sytem. Write a system of inequalities corresponding to the students graph. Explain how you arrived at your answer.

there is no isbn because this is a module book question

Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
There are two lines graphed, so we need to find the equations of those two lines first. From there, we can find the inequalities.


Line 1: Line going through points (0,4) and (4,0)


So let's find the equation of line 1


First let's find the slope of the line through the points and


Start with the slope formula.


Plug in , , , and


Subtract from to get


Subtract from to get


Reduce


So the slope of the line that goes through the points and is


Now let's use the point slope formula:


Start with the point slope formula


Plug in , , and


Distribute


Multiply


Add 4 to both sides.


Combine like terms.


Simplify


So the equation that goes through the points and is



-------------------------------------------------------


Line 2: Line through the points (0,0) and (3,6)


So let's find the equation of line 2



First let's find the slope of the line through the points and


Start with the slope formula.


Plug in , , , and


Subtract from to get


Subtract from to get


Reduce


So the slope of the line that goes through the points and is


Now let's use the point slope formula:


Start with the point slope formula


Plug in , , and


Distribute


Multiply


Add 0 to both sides.


Combine like terms.


Remove the trailing zero


Simplify


So the equation that goes through the points and is



===================================================


So the system of equations(we'll convert them into inequalities later) is:





Now, notice how the shaded region is BELOW both of the lines. In other words, EVERY point in the shaded region has a y-coordinate that is less than a point on either line.


So this means that we can take and convert it to (since every point in this shaded region is below the line ) and we can take and convert it to (since every point in this shaded region is below the line )


So we then end up with the system of inequalities




Note: If you are INCLUDING the boundaries, then you need to change the inequality signs from to like this:



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