Is that how it should be written, the portion in red?
Or like this:
The color option isn't working. Which line is how it should be shown, thanks.
Everything you've written looks fine.
If you are worried about the expressions like:
This is well understood to be addition of functions:
So in this case:
which is exactly what you want.
However, you are missing the step rewriting:
This will allow the expression to match the linear operator format exactly without missing an intermediate step.