> 
> There are 4 points: $A(0, -1, 5)$, $B(1, 3, 3)$, $C(5, 4, 0)$ and $D(3, 0, 4)$.
>  The first plane($\pi\_1$) contains the points $A$, $B$ and $C$.
>  The second plane ($\pi\_2$) contains the points $A$, $B$ and $D$.
> 
> 
> Find the Cartesian equation of the line where $\pi\_2$ intersects $\pi\_1$.
> 
> 
> 

I just need the concept of how to find that line. Should that be a comparison between $\pi\_1$ and $\pi\_2$ cartesian equations?