SOLUTION: need help on this one please complete the square and write the given equation in the standard form for the equation of a circle. then give the center and redius of the circle and

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: need help on this one please complete the square and write the given equation in the standard form for the equation of a circle. then give the center and redius of the circle and       Log On


   

Question 62309: need help on this one please
complete the square and write the given equation in the standard form for the equation of a circle. then give the center and redius of the circle and sketch a graph
x^2 + 8x + y^2 + 4y + 16= 0
Answer by funmath(2933) About Me  (Show Source):
You can put this solution on YOUR website!
Complete the square and write the given equation in the standard form for the equation of a circle. then give the center and redius of the circle and sketch a graph.
x^2 + 8x + y^2 + 4y + 16= 0
x^2+8x+___+y^2+4y+___=-16+___+___
We need to fill the blanks with (b/2)^2 from each square we wish to complete. Whatever you do to one side you have to do to the other side.
The first set of blanks get (8/2)^2=4^2=16 the second get (4/2)^2=(2)^2=4
x^2+8x+16+y^2+4y+4=-16+16+4
(x^2+8x+16)+(y^2+4y+4)=4 Factor
%28x%2B4%29%5E2%2B%28y%2B2%29%5E2=4<---standard form of the equation of the circle.
The standard form of a circle is: highlight%28%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2%29, where (h,k) is the center and sqrt%28r%5E2%29=r is the radius.
For this circle the center is (-4,-2) and the radius is sqrt%284%29=highlight%282%29

Happy Calculating!!!