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Let line L1  be the graph of 5x + 8y= -9. Line L2 is perpendicular to line L1 and passes through the point (10, 10). If line L2 is the graph of the equation y = mx + b, then find m + b.

 Aug 25, 2018
 #1
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5x + 8y  = -9

In the form  ax + by  = c, the slope of this line  is   -a/b = -5/8

 

So...a perpendicular line will have a negative reciprocal slope  = - (-8/5)  = 8/5

 

So......the equation of a line with  a slope of  8/5  passing through (10,10) is

 

y =(8/5)(x - 10) + 10

y  =(8/5)x - 16 + 10

y = (8/5)x  -  6

 

So.....m =  8/5    and   b   = -6  =  -30/5

 

So....m + b   =     8/5  - 30/5  =    -22/5

 

 

cool cool cool

 Aug 25, 2018

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