(x+20) ​2 ​​ +(y−30) ​2 ​​ =225space, left parenthesis, x, plus, 20, right parenthesis, start superscript, 2, end superscript, plus, left parenthesis, y, minus, 30, right parenthesis, start superscript, 2, end superscript, equals, 225 a circle in the xyxyx, y-plane has the equation shown above. what is the yyy-coordinate of the center of the circle?