My teacher hasn't taught me this its just in the book that i'm working from.
And why does everything have to depend on a teacher
Indeed.
If you're working through a book then it's almost definitely the case that the question you're being asked can be solved using material introduced in the preceding chapters. If the quadratic formula hasn't been introduced in the book before this question is asked, then it's likely that, at the very least, the method of completing the square has been introduced. So on that assumption, you could complete the square to get the answer.
If you're still unsure, flick through the book to find out how to solve quadratic equations.
My teacher hasn't taught me this its just in the book that i'm working from.
And why does everything have to depend on a teacher
If you don't want to depend on a teacher then surely you need to actually read the bit in the book that teaches this bit. If it's asking questions without previously explaining how to tackle these questions I suggest you get a new textbook.
He is using various phrases to get us to teach him. He seems keen but unfortunately not keen enough to use a textbook or google.
I know, I agree that he needs to be a bit more independent or use his teacher.
After all OP, this forum is for helping people when they struggle; not for outright teaching things. If you had read up about the quadratic equation but got stuck on this question then that's fine. But it's like you're not trying.
x²-6x = (x-3)²-9 <--- since (x-3)² = x²-6x+9, you have to take 9. ------------------------------ Notice: (x-3)²... half of the 6 from x²-6x. (x-3)² -9=-2 <---- Equate this back to x²-6x=-2