SOLUTION: Center at (2,-1) and passing through (-1,2)

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Question 1014485: Center at (2,-1) and passing through (-1,2)
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
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Find radius (distance from center to point on circle)
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P%5B1%5D=center=(2,-1); P%5B2%5D=(-1,2)
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d=sqrt%28%28x%5B2%5D-x%5B1%5D%29%5E2%2B%28y%5B2%5D-y%5B1%5D%29%5E2%29
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r=sqrt%28%28-1-2%29%5E2%2B%282-%28-1%29%29%5E2%29
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r=sqrt%28%28-3%29%5E2%2B%283%29%5E2%29
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r=sqrt%289%2B9%29
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r=3sqrt%282%29
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Equation for circle:
center=(h,k)=(2,-1)
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%28x-h%29%5E2%2B%28y-k%29=r%5E2
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%28x-2%29%5E2%2B%28y%2B1%29%5E2=%283sqrt%282%29%29%5E2
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%28x-2%29%5E2%2B%28y%2B1%29%5E2=18
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CHECK:
Substitute point (-1,2) for x and y.
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%28x-2%29%5E2%2B%28y%2B1%29%5E2=18
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%28-1-2%29%5E2%2B%282%2B1%29%5E2=18
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%28-3%29%5E2%2B%283%29%5E2=18
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9%2B9=18
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18=18