ListPlot with Joined set to True

Question

Let

f[x_]=9x^2-2x-3;

I want to make a table of f at x ={-1, -0.5, 0, 0.5, 1, 1.5, 2}. Plot these values with ListPlot + option Joined set to True Make a "normal" plot of f on the interval [-1, 2]

---

Table[{f[x]}, {x, -1, 2, 0.5}]

Curves := Riffle[Table[{f[x]}, {x, -1, 2, 0.5}], Table[{f[x]}, {x, -1, 2, 0.5}]]
ListLinePlot[Curves]
Plot[f[x], {x, -1, 2}]

Is this ok for this task? Because i think with Joined the points dont get joined but are still separate, but I don't know if that's normal because of ListPlot. And with Plot I don't think I got the right function, but if I do:

Plot[f[x], {x, -1, 2}]

then I miss the points $-.5, .5, 1.5$. Or shouldn't that be a problem since the question is not that specific?

Thanks in advance!

Answer 1

It seems you want to do something like this:

f[x_] = 9 x^2 - 2 x - 3; 
 Curves = Table[{x, f[x]}, {x, -1, 2, 0.5}]; 
 Show[{
     ListLinePlot[Curves, PlotStyle -> Red, 
     Epilog -> {AbsolutePointSize[Large], Point /@ Curves}] , 
 Plot[f[x], {x, -1, 2}, PlotStyle -> Dashed]
 }]

which shows the difference between the Built in Plot and ListLinePlot routines.