Let $f(x) =\dfrac{x+3}{x-1}$ and $g(x)=x^3+x^2-6x$.
The graphs of $y=f(x)$ and $y=g(x)$ are shown below. The point $(a,b)$ is on the graph of functions $f$ and $g$ and is on the $x$-axis.

**The value $x=a$ is a solution to which of the following equations?**
[[☃ radio 1]]