This question shows you are not familiar with the subject. My advice is that you should read your textbook/notes again. Work out few simple problems.And also, I'm confused about this.. is -tanx-tanx equal to -2tanx or -tan2x?

By the way -tan x -tan x = -2 tan x

I will answer your question, but I doubt you will understand every step clearly. First read the identities and know them clearly and then re read my post, you will understand the solution.

For the first equality, I have used the relation

For the second equality I have used