(x^2-4x)+(y^2+6y)-3=0
(x^2-4x+4)-4+(y^2+6y+9)-9-3=0
(x-2)^2+(y+3)^2=16
C(2;-3) - центр
R=4
б)
(3x^2+6x)+(3y^2-4y)-2=0
3(x^2+2x)+3(y^2-(4/3)y)-2=0
Делим на 3
(x^2+2x)+(y^2-(4/3)y)-(2/3)=0
(x^2+2x+1)-1+(y^2-2*(2/3)y+(2/3)^2)-(2/3)^2-(2/3)=0
(x+1)^2+(y-(2/3))^2=19/9
С(-1;2/3)-центр
R=sqrt(19)/3