Calculating Value of Inverse function

Hi

I have the function f(x) = x^2/(1+sqrt(x)) and I am trying to calulate the value of the invrese function at 2 i.e. F^-1(2)

I am trying to use 'finverse' but and have succefulle extracted the inverse function and seperatley calculating the value but nor during the same attempt.

this is the latest attempt

sym x

x = 2;

g = finverse(x.^2./(1+sqrt(x)),x);

f = @(x) g;

disp(f(2))

Answer 1

[VBBV]

syms x
g = finverse(x.^2./(1+sqrt(x)),x);
% x = 2;   
f = @(x) g;
disp(f(2))

[VBBV]

syms x
g = finverse(x.^2./(1+sqrt(x)),x);
% x = 2;   
f = @(x) g;
double(subs(g,x,2))

ans = 2.2336

Answer 2

[Sam Chak]

Hi @Johan Ahlberg

How about this?

syms x
f(x) = (x^2)/(1 + sqrt(x));
g = finverse(f)

g(x) = 

double(g(2))

ans = 2.2336

[Johan Ahlberg]

You are getting the answer I am looking for but for some reason I am getting the following error

Error using sym/subsindex

Invalid indexing or function definition. Indexing must follow MATLAB

indexing. Function arguments must be symbolic variables, and function

body must be sym expression.

Error in A_3_1_31 (line 3)

f(x) = (x^2)/(1 + sqrt(x));

[Sam Chak]

It thinks you used symbolic variable "x" as indices

syms x
x = 2;      % <--- because of this line
f(x) = (x^2)/(1 + sqrt(x));
g = finverse(f)

You can comment out it.

[Johan Ahlberg]

Copied your code directly and got that error

[VBBV]

clear

check the workspace variables if it has x value assigned to 2, use clear and try again

[Sam Chak]

Hmm... This is strange. No error on mine.

Perhaps try clearing the variables from your Workspace. Then test the code again.

Have you tried @VBBV's code on your MATLAB?

[Johan Ahlberg]

Clearing the workspace worked, my bad.