"Complete the square" to convert the equation of each circle to graphing form. Identify the center and the radius.

x² + 6x + y2 – 4y= -9

Respuesta :

Answer:

The center is (-3,2) and the radius is r=2

Step-by-step explanation:

The general equation of the given circle is

[tex]x^2+6x+y^2-4y=-9[/tex]

Add the square of half the coefficient of the linear terms to both sides of the equation to obtain;

[tex]x^2+6x+3^2+y^2-4y+(-2)^2=-9+3^2+(-2)^2[/tex]

[tex]x^2+6x+9+y^2-4y+4=-9+9+4[/tex]

[tex]x^2+6x+9+y^2-4y+4=4[/tex]

The quadratic trinomials in x and y on the left side of the equations are perfect squares.

We factor to obtain;

[tex](x+3)^2+(y-2)^2=4[/tex]

[tex](x--3)^2+(y-2)^2=2^2[/tex]

Comparing to:

[tex](x-h)^2+(y-k)^2=r^2[/tex]

The center is (-3,2) and the radius is r=2