Need help with algebra

label Algebra
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The equation of a circle is (x + 12)2 + (y + 16)2 = (r1)2, and the circle passes through the origin. The equation of the circle then changes to (x – 30)2 + (y – 16)2 = (r2)2, and the circle still passes through the origin. What are the values of r1 and r2?

A)

B)

C)

D)

May 11th, 2015


 

If the origin (0,0) is a point on (x+12)2 + (y+16)2 = (r1)2 then 

(r1)2 = (0+12)2 + (0+16)2 = 144 + 256 = 400 so 

r1 = +√400 = 20 

Similarly for 

(r2)2 = (0-30)2 + (0-16)2 = 900 + 256 = 1156 so 

r2 = +√1156 = 34 


May 11th, 2015

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May 11th, 2015
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