Substitution after differentiation (easy)?

I am trying to substitute the variable x after differentiating y with respect to x. Any ideas on the final step?

>> syms x;

>> y=5*x^2+6*x-3;

>> y1=diff(y,x);

after this I cannot use

>> x=3;

>> y1

because this just gives me y1 in terms of x

Answer 1

[Walter Roberson]

subs(y1)

Caution: the result in this case would be a symbolic number; use double() on the result if you need a floating point number that MATLAB itself can compute with.