How to do manual operation of cross multiplication or substitution?

If

syms A B x
y = A*x^2 + B*x;
dy = diff(y)
d2y = diff(dy)

then how to get where d2y is the second derivation; using subs or any other command in MATLAB

Answer 1

[Chunru]

Is this what you want?

syms A B x z
y = A*x^2 + B*x;
dy = diff(y)

dy = 

d2y = diff(dy)

d2y = 

z = d2y/x^2

z = 

[Muhammad Usman]

Please suggest me automate the operation

z = d2y/x^2

not manually.

Thanks

[Chunru]

What do you mean "automate the operation"?

[Muhammad Usman]

Means using any built-in command like subs or eval

[Chunru]

subs and eval are for different purposes (not in your questions)