Factor the following. ( correct and best explained answer gets brainliest : )

The answer is (x - 10)(x - 9).

Alright, so here is my thought process as I factored this out. 

The middle number, or second term, is the sum of the numbers within the parentheses after you factor. In this case, we had to get to -19.

Now, to figure out which two number are gonna add up to that, you need to figure out the factors of the last number in the equation, which is the constant. In this case, multiple choice tells us that 10 and 9 have got to be the factors of 90 we're looking for. 

Now, back to the first step. We have the numbers 10, 9, and -19. The only way to make 10 and 9 add up to -19 is by making 10 and 9 both negative. So -9 and - 10. 

Finally, you add the x's and the parentheses to make the lovely factored version of the equation: (x - 10)(x - 9)! :)