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avatar+386 

The answer provided by my book is:

 

( sqrt(2) -9) x  - 2y -3(sqrt(2) ) +45 = 0

 

Here is what I did with those two coords so far:

 

y=mx+b

 

9=3m+b    

 

Solve for m:

 

m=(9-b)/3

 

Replace in formula with coord ( 5, sqrt(2) ):

 

sqrt(2) = 5m + b

 

sqrt(2) = 5 ( (9-b)/3 ) + b

 

Solve for b:

 

b = 45 - 3( sqrt (2) )

 

 

So now I have both m and b values

 

Wouldn't the equation of the straight line be :

 

y =  ( (9-b) / 3 ) x  + ( 45 -3 ( sqrt (2) ) )

 

??? I'm confused as to what the book provides as the answer...

 Dec 19, 2016
 #1
avatar+37084 
+5

y= mx + b   = equation for a line

 

m= slope = (y2-y1)/(x2-x1) =  (sqrt2-9)/(5-3) = (sqrt2-9)/2

 

y = (sqrt2-9)/2  x    +  b

9 = (sqrt2-9)/2  (3) + b

9 = (3 sqrt2-27)/2 + b

b =  9 - (3sqrt2-27)/2

   =  18/2  - (3sqrt2)/2 + 27/2

b= 45/2 - (3sqrt2)/2

 

so equation becomes    y = (sqrt2-9)/2  x  +   45/2  - (3sqrt2)/2       Multiply everything by '2'

2y = (sqrt2-9)x + 45 - (3sqrt2)      subtract 2y from both sides and you will see your answer !

 Dec 19, 2016

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