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Sorry, I am a beginner of Mathematica, try to plot a function, my short code is as follow, but the pic is blank. I could not find what is wrong in my code. Thanks a lot!

f[x_] := x + 2^0.5*x^1.5
g[x_] := InverseFunction[Composition[f, f]][x]
k[x_] := x^0.5*g'[x]/g[1]
Plot[k[x], {x, 0, 1}]
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  • $\begingroup$ replace g (1) with g[1] in line 3 of your code. $\endgroup$
    – kglr
    Jan 17, 2018 at 15:12

1 Answer 1

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f[x_] = x + 2^(1/2)*x^(3/2);

g[x_] := InverseFunction[Composition[f, f]][x]
k[x_] := x^(1/2)*g'[x]/g[1]

Plot[Evaluate@k[x], {x, 0, 1}, WorkingPrecision -> 15]

enter image description here

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  • $\begingroup$ Thanks for your help @Bob Hanlon. I try to iterate f[x] 4 times, my code is as follow, but encounter three problems: 1. the picture of this function goes below 0, it becomes partially negative, which is impossible since g[x] is increasing function. 2. the picture of k[x] is not 0 when x closes to 0, but it is obvious that k[0]=0 3. If I change the number slightly, just like below, the pic I plot is still blank f[x_] = x + 2^(1/3)*x^(4/3); g[x_] := InverseFunction[Composition[f, f, f, f]][x] k[x_] := x^(1/3)*g'[x]/g[1] Plot[Evaluate@k[x], {x, 0, 1}, WorkingPrecision -> 100] $\endgroup$
    – yewfeng so
    Jan 17, 2018 at 17:44

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