I have a bunch of these factoring problems to do, and some of them I can get myself (especially those with GCF or that are perfect squares or cubes). This one I am having trouble with:
Factor completely:
5x^2 – 38x – 16
Can someone please tell me how to factor this. I am not just looking for homework answers, I want to be able to do the rest myself. I will choose a best answer, I always do. Please and thank you, very much.
2007-03-11 14:09:18 · 3 answers · asked by Brackish 1 in Science & Mathematics ➔ Mathematics
Multiply 5 times -16 to get -80.
What two numbers when multiplied together will produce -80 but when added will give you the middle coefficient, which in this case is -38? See it?
How about -40 times 2?
Yes, that works! So, -40 (2) = -80 but -40 + 2 = -38.
We now set in groups:
5x^2 - 40x = Group A
2x - 16 = Group B
Factor each group.
Groups A:
5x^2 - 40x becomes 5x(x - 8).
Group B:
2x - 16 becomes 2(x - 8)
Do you see the quantity (x - 8) twice?
You only need one of them.
Final answer:
(5x + 2) (x - 8)
Guido
2007-03-11 14:18:02 · answer #1 · answered by Anonymous · 0⤊ 0⤋
First, you know that you will have a positive and a negative number because of the -16.
(5x + )(x - ) = 0
Next, you will need to find two factors of 16 that when multiplied with 1 and the other with 5, the result will be - 38.
Therefore:
(5x + 2)(x - 8) = 0
Set both to zero and solve.
2007-03-11 21:12:26 · answer #2 · answered by sillyboys_trucksare4girls 2 · 0⤊ 0⤋
Find factors of 5 and 16. The sign in front of the 16 isnegative, so the factors must be different and subtract to get -38 in the middle.
(5x + 2 )(x - 8 )
FOIL, 5x(8) = -40x; 2(x) = 2x Add to get -38x in the middle.
2007-03-11 21:13:59 · answer #3 · answered by richardwptljc 6 · 0⤊ 0⤋