If $6a^2-3b^2-c^2+7ab-ac+4bc=0$, then the family of lines $ax+by+c=0$ is concurrent at
- $(-2,-3)$
- $(3,-1)$
- $(2,3)$
- $(-3,1)$
Multiple answers are possible.
I am not able to group terms of the expression $6a^2-3b^2-c^2+7ab-ac+4bc=0$ so as to get expression in the form $\lambda_1L_1+\lambda_2L_2=0$, where $L_1$ and $L_2$ denote two lines out of the given family. Please help.