An equation of a circle is x^2 + y^2 + 10x – 6y + 18 = 0. Show all your work in determining the center and radius of this circle. In complete sentences, explain the procedure used.

Question

abb0t · Answer

The form of the circle is: $$(x-h)+(y-k) = r^2 $$
where (h,k) is the center of the circle, and r is the radius.
What you want to do is rearrange it to get it in that form. Use algebra to group (not combine) like terms. Then complete the square

anonymous · Answer

what is h and k in this equation?

abb0t · Answer

Well, that's up to you to figure out. First, group like terms:
$$(x^2+10x)+(y^2-6y)+18 = 0$$
Then, proceed to complete the square for x and y to get it in the form I stated earlier. Does that make more sense?

abb0t · Answer

To complete the square:
$$ax^2+bx + e$$ you add to both sides (including product side): $$(\frac{ b }{ 2 })^2 $$

anonymous · Answer

i know how to complete the square

abb0t · Answer

gotcha.