`ContourPlot` gives you an idea of the answer I think
   
    f[x_] = x*Cos[x]
    g[x_] = CubeRoot[-5 + (x)^2]
    h[x_] = Abs[x + 2]

    ContourPlot[f[g[x]] - h[f[x]] == (a)^2, {x, 0, 5}, {a, -1, 1}, FrameLabel -> {x, a}]

[![enter image description here][1]][1]

 


  [1]: https://i.sstatic.net/KUijm.png