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Thread: FACTORING TRINOMIALs

  1. #1
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    FACTORING TRINOMIALs

    25a2 +9b2 + 30ab

    2x2 - 16x + 32

    5c2 +30c + 45

    128x2 +96xy + 18y2

    450a2 +242c2 + 660ac

    y2 - xy - 56x2


    Can you show me how to do these promblems. I realy what to now how to learn to do theses problems.
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  2. #2
    Bar0n janvdl's Avatar
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    Quote Originally Posted by frow4 View Post
    25a2 +9b2 + 30ab

    2x2 - 16x + 32

    5c2 +30c + 45

    128x2 +96xy + 18y2

    450a2 +242c2 + 660ac

    y2 - xy - 56x2


    Can you show me how to do these promblems. I realy what to now how to learn to do theses problems.
    We did a bunch for you this afternoon. Can you please show us some of your work now? What have you tried?
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  3. #3
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    i can do simple ones like

    x2n + 10xn + 16

    (x^n + 8)(X^n+2)

    y2x - yx - 20

    (y^x-5) (y^x-4)

    what i am having troubles on

    128x2 +96xy + 18y2 ; 450a2 +242c2 + 660ac

    because of the x^2 and Y^2 and xy I have no idea what to do with those powers
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  4. #4
    Bar0n janvdl's Avatar
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    Quote Originally Posted by frow4 View Post
    y2 - xy - 56x2
    I'll do this one for you.

    The coefficient of $\displaystyle y^2$ is 1.

    So we can say this:

    $\displaystyle y^2 - xy - 56x^2 = (y + \text{something})(y - \text{something})$

    Now take a look at 56. We want factors of 56 so that the difference of the two factors gives us -1

    7 and 8 clearly satisfies this condition.

    So the final answer is:

    $\displaystyle y^2 - xy - 56x^2 = (y + 7x)(y - 8x)$
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  5. #5
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    Quote Originally Posted by frow4 View Post

    128x2 +96xy + 18y2

    So You times 128 by 18 to get 2304. factors of 2304 That equals 96 is 48.

    So it (128x+48y)^2

    then you reduces it to
    (8x+3y)^2

    Is that right
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  6. #6
    Bar0n janvdl's Avatar
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    Quote Originally Posted by frow4 View Post
    So You times 128 by 18 to get 2304. factors of 2304
    Why are you doing this?

    128x2 +96xy + 18y2

    First factor out a 2.

    $\displaystyle = 2(64x^2 + 48xy + 9y^2)$

    $\displaystyle = 2(8x + 3y)(8x + 3y)$

    $\displaystyle = 2(8x + 3y)^2$
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  7. #7
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    Quote Originally Posted by Soroban View Post
    .

    Example: $\displaystyle 6x^2 - 35x + 36$

    Write the two pairs of parentheses and "split the x's": .$\displaystyle (\;x\qquad)(\:x\qquad)$

    Use the first coefficient twice: . $\displaystyle (\overbrace{6x}^\downarrow\qquad)(\overbrace{6x}^\ downarrow\qquad)$


    Multiply the first coefficient by the last coefficient: .$\displaystyle 6 \times 36 \,=\,216$

    We will factor $\displaystyle 216$ into two parts.
    Note the sign of the last term.
    . . If "+", think sum.
    . . If "-", think difference.
    i look this up and it tells me to do it
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