Please explain: xe^2+ye^2+6x-8y+20=0 represents a circle, find the center and radius.

Question

solomonzelman · Answer

please correct the typos

phi · Answer

leave out the "e's"
x^2+y^2+6x-8y+20=0
or
$$ x^2+y^2+6x-8y+20=0 $$

anonymous · Answer

x squared+ y squared+6x-8y+20=0

phi · Answer

to find the center we write the equation as
$$ (x^2+6x )+ (y^2-8y ) =-20 $$

in other words, reordered so the x's are next to each other, and the same for the y's
also, add -20 to both sides so that the "constant" is on the right-hand side.

phi · Answer

next, do you know how to "complete the square" ?

anonymous · Answer

no

phi · Answer

It is hard to explain here, but if you have time see https://www.khanacademy.org/math/algebra/quadratics/completing_the_square/v/solving-quadratic-equations-by-completing-the-square because the idea is complete the square for x^2 +6x and then do it again for y^2 -8y

anonymous · Answer

ok thank for your help i'll redo until i get it..thank again