Given below is the graph of a function $y=f(x)$.
\n{graph_cubic(a,b,c,d)}
", "advice": "The derivative at $x$ corresponds to the slope of the tangent line to the graph at the point $(x,f(x))$. In the figure below, we have drawn the line with slope $\\var{y0prime}$ through the origin in blue. We have also drawn a tangent line (in red) to the graph that is parallel to it and where the point of tangency has an $x$-value from the choices offered.
\n{graph_cubic_and_lines(a,b,c,d,x0,y0,y0prime)}
\nWe see that the correct choice is $\\var{x0}$.
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