x^2 + 10x + y^2 = 0
Complete the square for x
x^2 + 10x + 25 + y^2 = 25
(x + 5)^2 + (y-0)^2 = 5^2
A circle centered at (-5, 0) with radius 5.
2006-12-02 13:04:09
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answer #1
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answered by Jim Burnell 6
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Just to reiterate your question using more common notation on answers: x^2 + 10x + y^2 = 0
The general form of a circle is as follows;
(x-h)^2 + (y - k)^2 = r^2, with the coordinates of the center being (h,k) [note: you take the NEGATIVE of how h and k appear in the equation] and r being the radius.
In order to determine the center and radius of the above graph, i.e.
x^2 + 10x + y^2 = 0
You have to complete the square for the x terms. The term that would complete the square is 25, so you have to add 25 to the right hand side as well.
x^2 + 10x + 25 + y^2 = 0 + 25
(x+5)^2 + y^2 = 25
Thus, you now know the x-coordinate of the center; it's -5 (since the 5 in brackets is positive, and we take the negative of it). The y-coordinate of the center isn't immediately obvious, but note that
y^2 = (y+0)^2, so 0 is the y-coordinate of the center.
So the coordinates of the center are (-5,0).
To get the radius, you must consider that r^2 = 25 (i.e. the right hand side is supposed to contain the radius squared), so we just take the positive square root and find that r = 5. We discard the negative square root for this case because radii must be positive.
Therefore, to sketch the graph, you must first locate the point (-5,0), make a dot 5 points to the right, then make a dot 5 points up, then make a dot 5 points left, then make a dot 5 points down, and connect them to form a circle.
2006-12-02 21:09:02
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answer #2
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answered by Puggy 7
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(x+5)^2+(y)^2=25
center(-5,0)
radius=5 units
itis a circle
2006-12-02 21:06:24
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answer #3
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answered by raj 7
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