goggle docs & voicethreads

I could envision google docs and voicethreads to be used to send back feedback on students' assignments. If, for example, they submitted a homework assignment via an online class, I could review, correct, comment via voice threads or google docs. This would allow them to respond back to me also. Since this is math, formulas would have to be an integral part of creating the documents. Does either of these tools allow for equation editors to be used?