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Could someone please walk me through this factoring problem?
Now that I'm back in school, I've forgotten a few small things from last year, namely factoring. I have a few math problems I need to do that involve factoring, so I thought that if someone helped me solve it, it would help me remember what I need to do for the rest.
Thank you!
X^2 - 12X - 28
But how do you solve it? I need to show my work.
8 Answers
- PhilippeLv 61 decade agoFavorite Answer
(x - 14) (x + 2)
*Not much work needed...just need to follow some steps.
FOIL Method: (x ) (x )
Using this as a reference: x^2 + bx + c...which I'm sure you can correspond with the problem you gave.
IF c is positive, your factors are going to both have the same sign depending on b’s sign. Since it is not...then
Then, we need two numbers whose product is -28 and sum is -12. That would have to be -14 and 2...which leads to the answer on the top.
- Anonymous1 decade ago
Ask yourself this question: what adds to give me -12 and multiplies to give -28?
the fact that the last number, -28, is negative, tells you that of the two numbers you are looking for, one is negative and ove is positive.
what multiplies to give 28?
1, 28
2, 14
3, 7
if one number is negative, do any of those add to -12?
1-28 = -27
2 - 14 = -12
3 - 7 = -4
so it is 2 and -14
Split the middle factor into the two numbers and go from there:
X^2 - 14X+2X - 28 -------> (X^2 - 14X)+(2X - 28) ---------> X(X-14) + 2(x-14) = (x+2)(x-14)
(x+2)(x-14) is your answer
(some people skip right to here, once they find the two numbers, but wait until you are more confident to do so..)
- vahucelLv 61 decade ago
When you have a quadratic function with roots x1 and x2, the factoring is
y = (x-x1)(x-x2)
You function y = x^2 -12x - 28 have the roots x1 = 14 and x2 = -2
Then the factoring is y = (x-14)(x+2) OK!
- WhyIsSkyBlueLv 41 decade ago
Ask yourself, which two numbers MULTIPLY to get -28 and ADD to get a -12?
2 and -14, right?
So put these in factored form:
(x+2)(x-14).
There you have it
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- 1 decade ago
Factor
Expression
X^2 - 12X - 28
Result
(X-14)(X+2)
Source(s): Me:) I'm in eight grade and have math honors I'm in love with math...but no a geek lol :) Welcome - JamieLv 71 decade ago
Below is a link to an article on WikiHow that may be able to help you solve this problem.
http://www.wikihow.com/Factor-Second-Degree-Polyno...
Good luck and I hope I helped you!
- Kung Fu ChampionLv 61 decade ago
Well, I know (-14)(2) = -28
and -14+2 = -12
Then you'll write it as:
(x-14)(x+2)