In quadratic equations, that can be factorised, how do we know which one of the factors is the negative number

Question

In quadratic equations, that can be factorised, how do we know which one of the factors is the negative number?

Answer 1

when you multiply back out what you've factored, it has to simplify back to the original equation, if it doesn't, switch the signs and try again...if you have x(sqyared) -2x-8 you would factor it to (x _2) (x _ 4) if you put the - with the 2 and the + with the 4 you'd come up with x(squared)+2x-8. I know that's a very basic example, but the best way I've found is to multiply out your answer, and see if you come up with the original problem. The more you do, the more naturally it will come. Hope this made sense :)