Jenny, we are wanting to do FOIL backwards here. Since our leading coefficient is 5, then one parenthesis will start with x and one with 5x.
Now, we have to come up with the other side. We need factors of -2 that when one is multiplied by 5 and they are added together, we get 9.
Our factors of -2 are 1 and -2 or -1 and 2, right?
If we multiply -2(5) and add 1, we get -10 + 1 = -9.
If we multiply 1(5) and add -2, we get 5 - 2 = 3.
If we multiply -1(5) and add 2, we get -5 + 2 = -3.
If we multiply 2(5) and add -1, we get 10 - 1 = 9.
Therefore, the last choice is part of our answer, but how do we place them? Let's try trial and error again.
(x +2) (5x -1) = 5x2 - x +10x -2 = 5x2 + 9x -2, which is what we started with!
So, our answer is (x +2) (5x - 1)
Let's try the other way just to make sure, though.
(x -1) ( 5x +2) = 5x2 + 2x - 5x -2 = 5x2 - 3x -2, which is not our original equation, so that doesn't work.
I hope this helps!
