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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. 

 Aug 25, 2020
 #1
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From x + 3y = -5, y = -x/3 - 5, so the slope of the line is -1/3. The slope of the new line is also -1/3, so y = -x/3 + B.  Pugging in x = 2 and y = -7, we get -7 = -2/3 + B, so B = -19/3.

 

Then the line is y = -x/3 - 19/3.  Then 3y = -x - 19, so 3y + x = -19.  We want the right-hand side to be 3, so we mutiply both sides by -3/19: -9/19*y - 3/19*x = 3.  Therefore, B - A = -19/3 - 3 = -28/3.

 Aug 25, 2020
 #2
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It's incorrect, but thank you. 

 Aug 30, 2020
 #3
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Guest had the right general idea but made the mistake of using x = 2 and y = -7, instead of x =-7 and y = 2.  If you use these last numbers you should get the correct answer.

 Aug 30, 2020

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