# Plot function but blank

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
Plot[k[x], {x, 0, 1}]

• replace g (1) with g in line 3 of your code. – kglr Jan 17 '18 at 15:12

## 1 Answer

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

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

Plot[Evaluate@k[x], {x, 0, 1}, WorkingPrecision -> 15] • 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 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 Plot[Evaluate@k[x], {x, 0, 1}, WorkingPrecision -> 100] – yewfeng so Jan 17 '18 at 17:44