Get the answers you've been looking for with the help of IDNLearn.com's expert community. Ask your questions and receive detailed and reliable answers from our experienced and knowledgeable community members.

Given the equation of a circle, x^2 + y^2 - 6x + 2y + 1 = 0, find the coordinates of the center and the length of the radius

Sagot :

Answer:

Center: (3,-1)

Radius: 3

Step-by-step explanation:

Given:

[tex]\displaystyle \large{x^2+y^2-6x+2y+1=0}[/tex]

First, we have to convert the following standard circle equation to this:

[tex]\displaystyle \large{(x-h)^2+(y-k)^2=r^2}[/tex]

where h is horizontal shift, k is vertical shift and r is radius.

That means we have to complete the square for both x-term and y-term.

Rearrange the equation:

[tex]\displaystyle \large{x^2-6x+y^2+2y+1=0}\\\displaystyle \large{(x^2-6x)+(y^2+2y+1)=0}[/tex]

For [tex]\displaystyle \large{y^2+2y+1}[/tex], can be converted to perfect square as [tex]\displaystyle \large{(y+1)^2}[/tex]. Hence:

[tex]\displaystyle \large{(x^2-6x)+(y+1)^2=0}[/tex]

For the x-terms, we have to find another value that can complete the square. We know that [tex]\displaystyle \large{(a\pm b)^2 = a^2 \pm 2ab + b^2}[/tex].

For [tex]\displaystyle \large{x^2-6x}[/tex] can be [tex]\displaystyle \large{x^2-2(x)(3)+3^2 \to x^2-6x+9}[/tex]. So our another value is 9.

[tex]\displaystyle \large{(x^2-6x+9-9)+(y+1)^2=0}[/tex]

From above, we add -9 because the original expression isn’t actual perfect square.

Separate -9 out of [tex]\displaystyle \large{x^2-6x+9}[/tex]:

[tex]\displaystyle \large{(x^2-6x+9)-9+(y+1)^2=0}[/tex]

Transport -9 to add another side:

[tex]\displaystyle \large{(x^2-6x+9)+(y+1)^2=9}[/tex]

Complete the square:

[tex]\displaystyle \large{(x-3)^2+(y+1)^2=9}[/tex]

Finally, we have our needed equation to find radius and center. The coordinate of center is defined as the point (h,k) from [tex]\displaystyle \large{(x-h)^2+(y-k)^2=r^2}[/tex] and the radius is defined as r.

Hence, from the equation:

The coordinate of center is (3,-1) with radius equal to 3.