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i believe i need to find three ordered pairs in order to graph i could find the first oredered pair shown in the desciption but i do not know how to find the re

graph the linear equation by solving for y first

-2x+5y=-15

+2x          +2x

      5y = 2x - 15

      /5      /5    /5

y=2/5x -3

1st oredered pairs of y=2/5x-3  is (0,-3)

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2 Answers

You worked everything out perfectly. So you have the following linear equation:

     y = (2/5)x - 3

The first ordered pair you found is (0, -3), which means that when  x = 0  then  y = -3.

So for the next ordered pair, pick an x and plug it into the equation to solve for y. 

For simplicity, let's solve for y when x = -5 and when x = 5:

     x = -5

               y = (2/5)(-5) - 3

               y = -2 - 3

               y = -5

     thus, this ordered pair is (-5, -5)

     x = 5

             y = (2/5)(5) - 3

             y = 2 - 3

             y = -1

    thus, this ordered pair is (5, -1)

In the formula y=mx +b, m = the slope of the line.  This is how the points on the line are plotted.  If you've found the first point is (0, -3) then since the slope is 2/5 2 = the movement on the y axis, and 5 = the movement on the x axis.  You can either move have the next point be up 2 and over 5 to the right from (0, -3) or down 2 and back 5 from (0, -3).  Therefore 2 other points that should work are (5, -1) and (-5, -5).  Plug both into your equation of y = 2/5x - 3 and you will see that both points fit into the line.

 

Another option is to plug any number in for x OR y in order to find new points.  An example would be to plug 5 in for x and solve for y: y = 2/5 (5) - 3.  y= 2 - 3 and y would then equal -1.

 

Please e-mail me if you are still confused, have further questions, or if you know someone who may be looking for a tutor this summer in the greater DC/Baltimore area!