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Find the value of B - A if the graph of Ax + By = 3 passes through the point (-7,2), and is parallel to the graph of x + 3y = -5.

 

 

 

IT ISN'T 2

 Jul 2, 2020
 #1
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Every line that is parallel to the line  x + 3y  =  -5  has the form  x + 3y  =  k

where diffierent values of k will give you different (but parallel) lines.

 

Placing the point  (-7, 2)  into  x + 3y  =  k     --->   (-7) + 3(2)  =  -7 + 6  =  -1   --->   k  =  -1.

 

So, the equation of the line that passes through  (-7, 2)  that is parallel to  x + 3y  =  -5

      is  x + 3y  =  -1.

 

To get this equation to have the form  Ax + By  =  3

                                             instead of  x + 3y  =  -1

 

we'll need to multiply the bottom equation by  -3:

     -3 [ x + 3y  =  -1 ]     --->     -3x + -9y  =  3

 

This makes  A = -3  and  B = -9.

 Jul 2, 2020

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