AB is any chord of the circle x^2 + y^2 -6x -8y -11 = 0 , which subtend 90^{o} at (1,2). If locus of mid-point of AB is circle x^2 + y^2 - 2ax - 2by - c = 0, then find the value of a+b+c.

Answer not matching. Please help.

AB is any chord of the circle x^2 + y^2 -6x -8y -11 = 0 , which subtend 90^{o} at (1,2). If locus of mid-point of AB is circle x^2 + y^2 - 2ax - 2by - c = 0, then find the value of a+b+c.

Answer not matching. Please help.

1 Like

Ans. is 7. I am getting 31. How did you do?

1 Like

I am getting 8 now. I didn’t realise that (1,2) was inside the circle, but still answer is given 7.

1 Like

i am getting 5 now, i did once again (a small mistake)

1 Like

oh, didn’t notice answer is 7…

1 Like

Ya I did the same. Answer might be wrong.

2 Likes

Let me try too.

1 Like

yes bro, let wait for others to respond

1 Like

Ya sure bro why not.

Nahi.I didn’t login to brilliant lol.

1 Like

i think this is wrong please ignore

@manan_uppadhyay @Aastik_Guru @Amish_1706 @Abhinav.08 @VenkatAmith @Seshank @Navjeet_Kohli

In this question i got that any line of form ax+by+c=0 such that a,b,c in AP will pass through (1,-2) but problem is with radical axis , if we could prove somehow or find radical axis via image method and prove it is also of form ax+by+c=0 such a,b,c are in AP then the point of intersection of both will be (1,-2) for both lines and answer will satisfy it. Sorry for image quality , idk how to take screenshot from pc.

1 Like

Bro L1 is the radical axis of S1 and S2

1 Like

Can you explain kaise ? I knew has to be of form ax+by+c but wasnt able to find it.

Ok got it sorry , image hain dono toh tangents from L1 will be equal on both