anyone?

thetomps

Junior Member
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Sep 26, 2005
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i am not sure what formula to use for this question, any one ???

Find the center and radius of the circle given by the equation

x^2 + y^2 + 10x - 8y - 8 = 0
 
Hello, thetomps!


i am not sure what formula to use for this question
Formula? . . . Just the general equation of the circle: . \(\displaystyle (x\,-\,h)^2\,+\,(y\,-\,k)^2\:=\:r^2\)

And we have to "hammer" our equation into that form.

Find the center and radius of the circle given by the equation
\(\displaystyle x^2\,+\,y^2\,+\,10x\,-\,8y\,-\,8\:=\: 0\)
We have: .\(\displaystyle x^2\,+\,10x\,+\,y^2\,-\,8y\:=\:8\)

Complete the square: .\(\displaystyle x^2\,+\,10x\) + 25 \(\displaystyle +\,y^2\,-\,8y\) + 16\(\displaystyle \:=\:8\) + 25 + 16

Factor and simplify: .\(\displaystyle (x\,+\,5)^2\,+\,(y\,-\,4)^2\:=\:49\)

Therefore: .Center (-5,4), Radius 7
 
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