On Matlab program.

I want to perform mathematical operations after I entered the function, but it did not work.

this My code:

func $=$ input$(\text{'}$f$($x$)=\text{'},\text{'}$s$\text{'})$; $\%$ Type x$^2+$x$-5$

f $=$ str$2$func$([\text{'}$@$($x$)\text{'}$ func$])$

Sol$=$diff$($f$,$x$).$

$\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_$

diff$($f$,$x$)$ doesnt work $,$ I want to perform the derivation of the mathematical operation.