What is the standard form of the equation of a circle with centre (3,-1) and which touches the y-axis?

1 Answer
Aug 1, 2018

(x-3)^2+(y+1)^2=9(x3)2+(y+1)2=9

or x^2+y^2-6x+2y+1=0x2+y26x+2y+1=0 in quadratic form.

Explanation:

As circle with center (3,-1)(3,1) touches yy-axis, its radius is equal to its abscissa i.e. 33, and hence standard form of the equation of circle is

(x-3)^2+(y-(-1))^2=3^2(x3)2+(y(1))2=32

or (x-3)^2+(y+1)^2=9(x3)2+(y+1)2=9

or x^2-6x+9+y^2+2y+1=9x26x+9+y2+2y+1=9

or x^2+y^2-6x+2y+1=0x2+y26x+2y+1=0