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Math Help - subtracting polynomials

  1. #1
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    subtracting polynomials

    7x+1 - x^2+3x-8
    i got x^2-4x+9 but my teacher said it was wronge. how do I correctly solve this problem?
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  2. #2
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    Hello,

    Where did the - go for x ?
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  3. #3
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    I am not sure why would the x^2 be negative i am so lost
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  4. #4
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    Quote Originally Posted by imbadatmath View Post
    I am not sure why would the x^2 be negative i am so lost
    Are you subtracting the entire last 3 terms? If not, the original expression you entered was:

    7x + 1 - x^2 + 3x - 8

    Grouping like terms and evaluating, we get:

    (7 + 3)x + (1 - 8) - x^2
    10x -7 - x^2

    Rearranging this into proper form, we get:
    -x^2 + 10x -7


    Does that make sense?
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  5. #5
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    there where only 2 polnomials 7x+1 minus x^2+3x-8
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  6. #6
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    Quote Originally Posted by imbadatmath View Post
    there where only 2 polnomials 7x+1 minus x^2+3x-8
    ok, then you should have written it like this:

    7x + 1 - (x^2 + 3x - 8)

    Now, distribute the negative sign for the second polynomial:

    7x + 1 - x^2 - 3x + 8

    Now group like terms:
    (7 - 3)x + (1 + 8) - x^2
    -x^2 + 4x + 9
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  7. #7
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    thanks alot
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