What is the value of b for the following circle in general form? x^2+y^2+ax+by+c=0

a = -2 and b=4 and c = -4

Step-by-step explanation:

the center is : A(1 ; -2)

B(1 ; 1) in this circle so ; AB= r  (  ridus)...r =3

note :

an equation of the circle Center at the A(1,-2) and ridus : r is :

(x-1)² +(y+2)² = 3²  

x²-2x+1  +y²+4y +4-9 =0

x²+y² -2x+4y -4 = 0   so : a = -2 and b=4 and c = -4