Differentiating a symbolic function

i want to differentiate f=@(x)x^3-4*x^2+x+6; how can i do this? how i can find f'(x)?

Answer 1

[KSSV]

syms x
f=x^3-4*x^2+x+6;
df = diff(f)

Answer 2

[Roger Stafford]

Express your function in symbolic form and use ‘diff’.