Passive voice vs. present perfect!
Just imagine that as a lecturer, I am presenting a topic, and I have some related slides.
Where the words are in bold face, I am in doubts. Would you please correct me?
"... as you can see, in [on or at] this slide, our calculation formula is written [or has been written/was written]. This formula is only for [or is for only] the situation that mentioned [has been mentioned/is mentioned/was mentioned] in [or without in] our last session. Also, the formula is explained [was explained/has been...] in your book on [at] page 100 ..."
Additionally, would you please explain briefly about the reasons of your correction?