How do you factor $2ab-6ac-15c^2+5bc$

Question

$$2ab-6ac-15c^2+5bc$$

Here is what I have done:

$$(2ab-6ac)-(15c^2+5bc)$$ $$2a(b-3c)-5c(3c+b)$$ $$2a(b-3c)+5c(-3c-b)$$ $$2a(b-3c)+5c(-b-3c)$$ $$(b-3c)(2a-5c)$$

I know this isn't the correct answer but I can't figure out what I did wrong. Could someone please explain this to me?

Answer 1

It should be $(2ab−6ac)−(15c^2-5bc)$ at the first line you have done.

Answer 2

Distributing your second line would give $2ab-6ac-15c^2-5bc,$ which is obviously not correct. Instead, it should be $+5c(-3c+b).$ Also observe that your last line should be $(2a+5c)$ instead of $(2a-5c)$ which would give you $(2a+5c)(b-3c).$