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find the center and radius of a circle whose equation is x^2 +y^2 -8y-9...Themeaning of this ^ is to the power of 2


Sagot :

convert the given equation into the form [tex] (x-h)^{2} [/tex] + [tex] (y-k)^{2} [/tex] = [tex] r^{2} [/tex]   where the center is (h,k) and r is the radius

in order to achieve this, use completing the square on the y value, the formula is (b/a)^2

so, youll have [tex] (x)^{2} [/tex] + [tex] (y)^{2} [/tex]-8y + 16= 0+9 +16 
add sixteen to the other side too so that you will not violate the equality law
then use factoring, youll get
(x)^{2} [/tex] + [tex] (y-4)^{2} [/tex] = 25

so, (0,4) as center and 5 as radius