Suppose I have a function of x with two parameters a,b : f(x;a,b).

I want to plot x'(a,b) where x' is the root of the above function .i.e f(x';a,b).

I know that for all a and b, the roots real.

How can I plot this over a range of a and b?

I feel like if I specify a resolution, then I'll just get a scatter plot of individual points. I'd like to get a smooth plot ideally.

  • 1
    $\begingroup$ Please include an example function and the parameter ranges to get a concrete answer. Thanks. $\endgroup$
    – Syed
    Commented Feb 9 at 18:20

1 Answer 1


(* "14.0.0 for Mac OS X ARM (64-bit) (December 13, 2023)" *)


f[x_, a_, b_] := a*x + b

root[a_, b_] = SolveValues[f[x, a, b] == 0, x][[1]]

(* -(b/a) *)

In 3D

Plot3D[root[a, b], {a, -5, 5}, {b, -6, 6},
 AxesLabel -> (Style[#, 14] & /@ {a, b, root}),
 ClippingStyle -> None]

enter image description here

In 2D

   Tooltip[root[a, b], b], {b, -6, 6}],
 {a, -5, 5},
 AxesLabel -> (Style[#, 14] & /@ {a, root}),
 PlotLegends -> LineLegend[Range[-6, 6],
   LegendLayout -> {"Column", 2},
   LegendLabel -> Style[b, 14]]]

enter image description here


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