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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

Update:

But how do you solve it? I need to show my work.

8 Answers

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  • 1 decade ago
    Favorite 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.

  • Anonymous
    1 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..)

  • 1 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!

  • 1 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
  • Jamie
    Lv 7
    1 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!

  • 1 decade ago

    Well, I know (-14)(2) = -28

    and -14+2 = -12

    Then you'll write it as:

    (x-14)(x+2)

  • 1 decade ago

    (x-14)(x+2)

    Hope that helps. :)

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