2006-06-15 10:53:43 · 12 answers · asked by Ez E 2 in Education & Reference ➔ Homework Help
Well, think of it this way:
What two numbers multiply to get -20?
-1 x 20, -20 x 1
-2 x 10, -10 x 2
-4 x 5, -5 x 4
Now which of those pairs adds together to give you -1 (because the coefficient of -x is -1)?
You can see that only -5 + 4 = -1!
Thus, the factors are (x - 5)(x + 4)
I hope this helps! :)
2006-06-15 10:57:16 · answer #1 · answered by snoopyagent007 2 · 5⤊ 0⤋
FOIL method = first, outer, inner, last
Multiply two numbers that will give you a 1 (for the middle x)
Well, 5 x 4 = 20 and 4 x 5 = 20.
Using the numbers 5 and 4, what operation would give you a -1?
Subtraction: 4 - 5 = -1
So use the two digits 4 and 5.
You know that x has to be 1 because 1 x 1 = 1; THEREFORE
(x - 5) (x + 4) is your answer
FIRST = x * x = X2
OUTER = 4X
INNER = -5x
operation is 4x -5x = -x
LAST = -5 X 4 = -20
2006-06-15 16:11:48 · answer #2 · answered by curlywurly007 2 · 0⤊ 0⤋
First factor the x2 into two parenthesis.
(x )(x )
Add the signs by looking at the sign in front of the twenty. Since it is a - the signs have to be different.
(x+ )(x- )
Now look for factors of 20 that subtract to 1.
You get that by looking at the sign in front of the twenty. Since it is a - you look for factors that SUBTRACT to one (if it was a + you would add). You get 1 because of the number in front of the x (1 is not shown, but it's there).
Factors of 20 that subtract to 1 are 4 and 5. The larger number goes with the - sign because of the sign in front of the x.
(x+4)(x-5)
2006-06-15 11:04:33 · answer #3 · answered by Lizzie 1 · 0⤊ 0⤋
Look at it in the form x2 + (-1)x + (-20) You need two numbers that add to -1 and multiply to -20.
Here, the factors are (x - 5)(x+4). Use FOIL to multiply it out and you'll see.
2006-06-15 10:56:18 · answer #4 · answered by -j. 7 · 0⤊ 0⤋
(x+4) and (x+5)
2006-06-15 10:59:14 · answer #5 · answered by bradybootoo 1 · 0⤊ 0⤋
(x-5)(x+4)
2006-06-15 10:59:51 · answer #6 · answered by Frank V 2 · 0⤊ 0⤋
(x-5)(x+4)
2006-06-15 10:55:54 · answer #7 · answered by Rasha S 3 · 0⤊ 0⤋
(x-5) (x+4)
x^2 + 4x - 5x - 20
x^2 - x -20
2006-06-15 10:59:04 · answer #8 · answered by L S 2 · 0⤊ 0⤋
oh how I miss high school algebra...NOT REALLY....I am so glad I am in college now and don't have to deal with that crap...you will never use it...I promise...4 years of college and I haven't seen a problem like that since junior year in high school....
2006-06-15 10:59:50 · answer #9 · answered by j_nelle_03 3 · 0⤊ 0⤋
(x-5) (x+4) right?
that's like pre-algerbra.
2006-06-15 10:56:03 · answer #10 · answered by Anonymous · 0⤊ 0⤋