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Math Help - simplifying multiplied trinomials

  1. #1
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    simplifying multiplied trinomials

    I can multiply this easily-but the problem says to simplify it. I have the answer and NO idea how to get there. Can someone help to simplify:

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

    Please show steps-I'm lost! Thanks!
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  2. #2
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    Quote Originally Posted by ab27834 View Post
    I can multiply this easily-but the problem says to simplify it. I have the answer and NO idea how to get there. Can someone help to simplify:

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

    Please show steps-I'm lost! Thanks!
    Multiply it. and then, look for like terms and simplify.
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  3. #3
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    did. doesn't match what the book says the answer is. i've gotten several people to look at it; they all come back with what I did. The book says the answer is 3x^3-10x^2+8x+11. I'm completely lost how that is.
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  4. #4
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    Quote Originally Posted by ab27834 View Post
    did. doesn't match what the book says the answer is. i've gotten several people to look at it; they all come back with what I did. The book says the answer is 3x^3-10x^2+8x+11. I'm completely lost how that is.
    Are you sure you typed it right? Is it  (3x^2-2x-7)(8x^2-8x+7) or  (3x^3-2x^2-7)(8x^2-8x+7)\;\;?

    Is this  (3x^2-2x^2-7)(8x^2-8x+7) the right question in your book? If it is then

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

    =(x^2-7)(8x^2-8x+7)

    =8x^4-8x^3+7x^2-56x^2+56x-49

    =8x^4-8x^3-49x^2+56x-49 is the simplified answer.

    answer in your book is wrong then.
    Last edited by Shyam; December 6th 2008 at 06:45 PM.
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