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Mathematics 8 Online
OpenStudy (anonymous):

determine the type of boundary line and shading for the graph of the inequality 5x+y>=-10 a.) dashed line with shading on the side that includes the origin b.)solid line with shading on the side that does not include the origin c.)dashed line with shading on the side that does not include the origin d.)solid line with shading on the side that includes the origin

OpenStudy (anonymous):

I know its either b or d

OpenStudy (phi):

yes, ≥ means a solid line. the origin means (0,0) which means x=0 and y=0 if you replace x and y with 0 in 5x+y ≥ -10 what do you get ?

OpenStudy (anonymous):

5>=-10

OpenStudy (anonymous):

5x*

OpenStudy (phi):

no... try again. remember 5x + y ≥ -10 means 5*x + y ≥ -10 erase the x, and put in 0. erase the y and put in 0 then simplify

OpenStudy (anonymous):

it is b because it has the origin that be multiplied by x

OpenStudy (anonymous):

@phi is it b?

OpenStudy (phi):

if you replace x and y with 0 in 5x+y ≥ -10 what do you get ?

OpenStudy (anonymous):

5(0)+0>=-10

OpenStudy (phi):

yes. can you simplify the left side ?

OpenStudy (anonymous):

5>=-10

OpenStudy (phi):

5(0)+0>=-10 5 times 0 plus 0 remember order of operations. First do multiply, then add so the first step is 5 times zero

OpenStudy (anonymous):

so would it be 0??

OpenStudy (phi):

yes, you get 0≥ -10 now, is that true ? Is 0 greater than or equal to -10 ?

OpenStudy (phi):

If it were temperature, is 0 degrees bigger (warmer) than -10 degrees ?

OpenStudy (anonymous):

yes

OpenStudy (phi):

if 0≥ -10 that means (0,0) makes 5x+y≥ - 10 true. you want to shade the side of the line that makes the equation true.

OpenStudy (anonymous):

okay so the answer is b?

OpenStudy (phi):

Here is what the line looks like.

OpenStudy (phi):

one side of the line (meaning all the points on that side) make the relation true. which side makes the relation 5x+y≥ - 10 true ?

OpenStudy (anonymous):

left?

OpenStudy (phi):

to answer the question, you pick a point (ANY POINT) on one side, and see if makes the relation true. If it does, then ALL the points on that side will make the relation true.

OpenStudy (phi):

A really easy point to test is (0,0) (the arithmetic is easy) if it "works" , that is the side you want to shade.

OpenStudy (anonymous):

sooooooo out of the four answers d would be correct?

OpenStudy (anonymous):

a.) dashed line with shading on the side that includes the origin b.)solid line with shading on the side that does not include the origin c.)dashed line with shading on the side that does not include the origin d.)solid line with shading on the side that includes the origin

OpenStudy (phi):

why ?

OpenStudy (anonymous):

because it should be a solid line that has the origin

OpenStudy (phi):

Here is how you would plot this problem

OpenStudy (anonymous):

im confused is it b or d?

OpenStudy (phi):

which side do you shade ? the left side or the right side ? which side is the origin on ?

OpenStudy (anonymous):

you shade the side with the origin?

OpenStudy (phi):

yes. which choice would that be?

OpenStudy (anonymous):

d

OpenStudy (phi):

notice if the problem were 5x+y ≤ - 10 the origin (0,0) would NOT WORK: 0 ≤ -10 is not true. You would shade the side that did not have the origin.

OpenStudy (anonymous):

thanks :)

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