Answer to Question #91538 in Geometry for Sajid

Question

Q. Choose the correct answer.
Q. If R1, R2 and R3 are radii of circles x2+y2-2x+2y-2=0, x2+y2+2x-2y-7=0 and x2+y2+4x-2y-11=0 respectively, then
a. R1>R2>R3
b. R2>R1>R3
c. R3>R2>R1
d. R3>R1>R2

Answer 1

General equation of circle is

x²+y²+2gx+2fy+c=0

And radius is given by ( g²+f²-c)^1/2

R1=(1²+1²+2)^1/2=2

R2=(1²+1²+7)^1/2=3

R3=(2²+1²+11)^1/2=4

Hence R3 >R2>R1

Option C is correct.