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Line \(l_1\) represents the graph of \(3x + 4y = -14\). Line  \(l_2 \) passes through the point \((-5,7)\), and is perpendicular to line \(l_1\). If line \(l_2 \)represents the graph of \(y=mx +b\), then find \(m+b.\)

 Nov 12, 2020
edited by Guest  Nov 12, 2020
 #1
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Line 1 has the equation of 3x+4y = -14. I'm going to change this into slope intercept form

 

4y = -14 - 3x

y = -3x/4 + 7/2 This shows that the slope is -3/4. A  function perpendicular to this would have a slope of 4/3. For 2 linear functions to be perpendicular their slopes must be negative reciprocals. 

 

So line 2 so far has the equation y = 4x/3 + b

The question gives that this function passes through point -5,7, and we can plug this into the equation

 

7 = 4(-5)/3 + b

7 = -20/3 + b

b = 7 + 20/3

b = 61/3

The question is asking for m + b

m = 4/3 and b = 61/3

m + b = 65/3

 Nov 12, 2020
 #2
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that isn't correct

 Nov 12, 2020
 #3
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You're right. It isn't correct. 

Guest Nov 12, 2020

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