Question

Question on circle

Answer 1

If ax^2 + by^2 +(a+b-4)xy -ax -by -20 =0 , find the center and radius

Answer 2

i know center is given by (-g, -f) and the radius by root(g^2 +f^2 -c )
but how to apply in this case

Answer 3

@ganeshie8 @hartnn

Answer 4

@ikram002p

Answer 5

@hartnn

Answer 6

circle equation has xy term ?? :O

Answer 7

yes actually that's what is bothering me

Answer 8

i think you're looking for center of curvatire and radius of curvature here ?

Answer 9

no gfanesh

Answer 10

it doesn't
a+b-4=0

Answer 11

yes i have written that in my notebook , but why i forgot

Answer 12

something cool u must know about circle , could u guess what is it /?

Answer 13

you're expecting a numerical answer ?

Answer 14

a=b

Answer 15

a=2 b= 2 , yeah why

Answer 16

for a circle
x^2 and y^2
co-efficients must be same

Answer 17

then equation can be found out easily

Answer 18

a=b
a+b=4
easiest system to solve :P

Answer 19

oh ye
and why a+b -4 =0

Answer 20

if this is a circle then a=b

Answer 21

circle equation cannot have xy term

Answer 22

ok i understand

Answer 23

The coefficient of x^2 must be the same as y^2 for it to be a circle

Answer 24

thank you ^_^

Answer 25

@ikram002p which property
@freckles yes i get i t

Answer 26

ikram, you were talking about a=b only, right ?

Answer 27

yep :P

Answer 28

both circle cant have xy term
and a=b , thats what i asked for xD

Answer 29

I do not know if a=b=2 though

Answer 30

It is because the general equation is
x^2 +y^2 +2gx + 2fy +c =0
if you observe there is no xy term here
so to make it 0 in the question
we put
a+b-4 =0

Answer 31

therefore we get that
a+b=4
since a=b
a =2 and b=2

Answer 32

there is no xy , cuz circle have no deviation , not like this

Answer 33

http://math2.org/math/algebra/conics.htm
I also know the general form to be Ax^2+Bxy+Cy^2+Dx+Ey+F=0
but I knever seen the conics with the xy term

Answer 34

Or I mean I have never seen the conics with the xy term in like actually examples