when you start out learning factoring you normally do it the harder way.
but there's some logic with factoring.
given , if the a is greater than one, you can do what's called the AC method.
For you first multiply the a and c.
That's -30. Since the linear term has a coefficient of +1, you need to find two numbers that multiply to give you -30 and add up to 1.
That's 6 and -5.
So rewrite this as:
Notice how I keep the -5x near the -15 since they have a common term.
Pull out a greatest common factor between terms:
Factor by grouping:
I might've went too fast, but we'll explain something more detailed if you ask the question.