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Does anyone know how to make a plot display (permanently and/or as tooltips) both the labels and values of the intersection points?

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  • $\begingroup$ If you could show your workings so far, we could take it from there. Additionally, depending on chosen implementation, I would recommend to look at Labeled[] and Drawing tools which are available by accessing Graphics>Drawing tools. $\endgroup$
    – e.doroskevic
    Dec 13, 2015 at 22:28
  • $\begingroup$ What do you mean by "Letters of the intersection points"? $\endgroup$
    – march
    Dec 13, 2015 at 23:15

1 Answer 1

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f[y_] := -10 y^2 + 4000 y;

Manipulate[
 Module[{pts, solQ},
  Column[{
    (pts = Cases[
        Simplify[
         {x, f[x]} /. Solve[f[x] == m*x + b,
           x, Reals]], _?(FreeQ[#, x] &)]) //
     N,
    solQ = Length[pts] > 0;
    Plot[{f[x],
      If[solQ, m*x + b, 0]},
     {x, 0, 400},
     PlotRange -> {{-10, 410}, {-10, 410000}},
     Epilog -> {Red, PointSize[Large],
       Tooltip[Point[#], #] & /@ pts,
       If[solQ, Text["A", pts[[1]], {1.5, -1.5}]],
       If[solQ, Text["B", pts[[-1]], {-1.5, -1.5}]]},
     ImageSize -> 360,
     PlotLegends -> {f[x], m x + b}]}]], {{m, 0, "Slope"}, -1000, 
  1000, 20,
  Appearance -> "Labeled"},
 {{b, 144000, "y Intercept"}, 0, 400000, 2000,
  Appearance -> "Labeled"}]

enter image description here

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  • $\begingroup$ Excellent answer, but I'd need a simpler solution. Thanks! $\endgroup$
    – puckie
    Dec 14, 2015 at 22:39

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