Error input must be floats, namely single or double.

tspan=[0:0.25:5];

syms x(t) m f_0

dx=diff(x)

x0=0;

ode=m*dx+k*x==f_0*sin(t)

[t,x]=ode45(@(t,x) ode,tspan,x0)

plot(t,x,'m')

Answer 1

[Walter Roberson]

Look at the documentation odeFunction for information on how to convert symbolic ode to numeric.