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Find all points $(x,y)$ that are $5$ units away from the point $(2,7)$ and that lie on the line $y = 5x - 28.$

 Sep 20, 2024
 #1
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  The set of points 5 units away from 2,7  is a circle :

(x-2)^2 + (y-7)^2 = 5^2  

 

The line might intersect at ONE point (tangent) or TWO Points .

   Plug in the value of the line into the circle equation 

      ( x-2)^2 + ( 5x-28 -7)^2 = 5^2 

Expand 

          x^2 - 4x + 4  + 25x^2 -350x  + 1225  = 25 

 Solve for 'x'

            26x^2 - 354 x + 1204 = 0    Use quadratic formula to find x = 7 and  6.61538   ( two points) ....use these values ofr 'x' in the line equation to find the corresponding ' y ' coordinates  = 7 and  5.07692

 

 Sep 20, 2024

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