The question is: If the curves $ax^2+4xy+2y^2+x+y+5=0$ and $ax^2+6xy+5y^2+2x+3y+8=0$ intersect at four concyclic points then the value of a is????
The options are:
a) 4
b) -4
c) 6
d) -6
I've tried to eliminate $ax^2$ and then proceed, but could not solve any further. I also asked my teacher for help, and he said to try and assume the four co-ordinates and use the equation of the circle that is formed. I don't understand what he meant and now he's unavailable.
Eliminate $xy$ from your equations instead.