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Math Help - Homework question

  1. #1
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    Homework question

    Hi everyone, first post here

    i'd appreciate it if anyone could help me with this question.

    If (x-2A)(2x+1)=2x2-Bx+10, then A B =

    thanks a lot

    if this is in the wrong subforum sorry, its precalc homework so i put it here
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  2. #2
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    Re: Homework question

    Hey Hell0.

    Hint: Try expanding both sides and multiply both sides by A so that you can match up the AB term and use the rest of the variables to solve for A,B (remember that in a quadratic, you have fx^2 + gx + c with three constants f,g,c).
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  3. #3
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    Re: Homework question

    Hi. this is what i tried


    x - 4Ax = -Bx

    and

    -2A = 10

    found a:

    A = -5

    then plugged it in:

    x - 4(-5)x = -Bx
    x + 20x = -Bx

    pulled out the x because they all have it:

    x + 20x = -Bx
    1 + 20 = -B
    -B = 21
    B = -21

    -21 * -5 = 105

    The answer is 105?
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  4. #4
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    Re: Homework question

    ( x- 2A )( 2x + 1 ) = 2x^2-Bx +10
    2x^2 +x - 4Ax - 2A = 2x^2-Bx +10
    2x^2 + ( 1 - 4A ) x - 2A = 2x^2-Bx +10
    Now compare the coefficients and conclude.
    You will get A*B = 105
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  5. #5
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    Re: Homework question

    hey thanks everyone. can you try to help me with this one? Pre-calc question? its the only blank question i have left. id really appreciate it
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  6. #6
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    Re: Homework question

    *solved*
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