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For what value of c will the circle with equation x^2 - 10x + y^2 + 4y + c = 0 have a radius of length 1?

 Oct 15, 2020
 #1
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Re-arrange to

x^2 - 10x + y^2 + 4y  = -c     now complete the squares for x and y

(x-5)^2      + (y+2)^2   = - c  + 25 + 4          The red portion = r2

 

-c + 25 + 4 = 12

29 = 1 + c

28 = c

 
 Oct 15, 2020

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