# SUBSTITUTIONS IN SYMBOLIC EXPRESSIONS

Hi,

I would like to know if it is possible to substitute expressions inside some equation or expression.

Consider the following expression:

$$(r+1)\cdot(r+2)+g+a$$

Then, I would like to say that I want this same expression for $c+d = 2\cdot r + a$.

Is this possible?

Can I implement something like this in SAGE?

I think you should explain a bit more what you are looking for. If, for example, you only want to replace $a$ in the expression by its value from the equality, you can simply do this: