How can I get outcome at a particular value after performing differentiation?

Hello,

I would like to know how I can get outcome at a particular value after performing "differentiation" of a function using Matlab code. For example, after obtaining the first derivative of the particular function x^2-2*x+6, substituting x=3 into the derivative, then the outcome will be 4. See the simple program I've constructed, and please let me know how to fix the error.

syms x
f=x^2-2*x+6;
diff(f,x=2)

Answer 1

[Walter Roberson]

subs(diff(f,x),x,2)

[onsagerian]

Thank you for your help!

Answer 2

[madhan ravi]

Another option:

dx(x)=diff(f);
dx(3)

[onsagerian]

Thank you for your help!