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April 18, 2014

Homework Help: college algebra--Please help Reiny please

Posted by ladybug on Friday, October 26, 2012 at 9:29pm.

You helped me with this question and this is what I got but my Professor says that each x and y intercept needs to have a coordinate. Where did I go wrong?? Can you help me?

x^2+y^2+4x+2y-20=0
x^2+4x+4+y^2-2y+1=20+4+1
(x+2)^2+(y+1)^2=25--this is where you helped me. Then I came and did the x and y intercepts. This what I got. But not a coordinate???

x-intercepts are found by setting y=0
(x+2)^2+(0-1)^2=5^2
x^2+4x+4+1=25
x^2+4x-20=0
x=[-4+/-sqrt((4^2)-(4)(1)(-20))]/2
=[-4+/-sqrt(96)]/2
[-2+/-2sqrt(6)]

y-intercepts are found by setting x=0
(0+2)^2 +(y-1)^2=5^2
y^2-2y+1+4=25
y^2-2y-20=0
y=[2+/-sqrt((-2^2)-(4)(1)(-20))]/2
=[1+/-sqrt(21)]

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