A certain circle can be represented by the following equation. x^2+y^2-2y-99=0x ​2 ​​ +y ​2 ​​ −2y−99=0x, start superscript, 2, end superscript, plus, y, start

Question

i also need the radius of the circle this is hard why 20 chatacters

Answer 1

Arrange all x-related terms in order, followed by all y-related terms, in order. Put the constant (signed appropriately) on RHS.

 

Complete the square twice, once in the "x department" and once in the "y department".  You will be creating new constants to the left side of this equation, in order to make perfect squares; do not forget to add those new constants to RHS also.

 

You wind up with (x-h)² + (y-k)² = r² and thus the center is at (h,k) and radius is r.