The order of the positives/negatives doesn't matter.

As for which one is positive/negative, that depends how you're factoring it.

If your equation was, say x^2+5-45 = 0 then you'd do it like this. (The 2x is a needless complication at this point, also, I'm assuming you mean x^2, not just x and that you meant -4x, not just -4.)

You need to find two numbers that add to 4, but multiply to -30.

In this case, those numbers are 9 and -5.

So, when you make your factors, you simply put the numbers into the brackets.

So, that equation factored is (x+9)(x-5).

If you aren't sure of your answer then it's easy enough to check, just multiply those brackets out.

x*x = x^2
x*-5 = -5x
-9*x = 9x
9*-5 = -45

Put those together and you get: x^2 -5x + 9x -45 = 0
Simplify that a bit, and you get: x^2 +4x - 45 = 0.

Since that equals the equation you started with it's factored correctly.