Why can't I do the integral?

syms x 
f=1/x
a=2
b=7

D1=diff(f,x);
D2=diff(D1,x);
D3=diff(D2,x);
D4=diff(D3,x);
E=(1/(b-a))*D4

F=int(E,a,b)

Error using sym/subsindex (line 857) 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 Untitled2 (line 12) F=int(E,a,b),

Answer 1

[Sulaymon Eshkabilov]

Clear up all variables should help or worst case, restrat your MATLAB. You may also need to have the floating point numbers in your answer. If so, use:

F=double(int(E,a,b))

Answer 2

[Girijashankar Sahoo]

%% run the program perhapes it work

F =

1431/19208