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Math Help - Expressions containing fractions and simplifying

  1. #1
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    Expressions containing fractions and simplifying

    I have an expression;

    (1 - u)(2u + 1/3) I am asked to multiply out the brackets and simplify. I am concerned about the fraction because I cannot find any examples in my course book to help with this type of expression.

    am I doing it correctly by this method;

    (1 - u)(2u + 1/3) = 2u + 3 - 2u^2 - 3u

    Thanks

    David
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  2. #2
    Super Member Quacky's Avatar
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    Re: Expressions containing fractions and simplifying

    Nearly.

    4\times{\frac{1}{3}}=\frac{4}{3}

    Just multiply the value by the numerator of the fraction.

    So what would:

    -u\times\frac{1}{3} be?

    Just FOIL it out as you normally would.
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  3. #3
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    Re: Expressions containing fractions and simplifying

    Quote Originally Posted by Quacky View Post
    Nearly.

    4\times{\frac{1}{3}}=\frac{4}{3}

    Just multiply the value by the numerator of the fraction.

    So what would:

    -u\times\frac{1}{3} be?

    Just FOIL it out as you normally would.
    - u Yes
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  4. #4
    Super Member Quacky's Avatar
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    Re: Expressions containing fractions and simplifying

    I'm confused by your response. Do you understand where you were going wrong?
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  5. #5
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    Re: Expressions containing fractions and simplifying

    Quote Originally Posted by Quacky View Post
    I'm confused by your response. Do you understand where you were going wrong?
    I will have to look up FOIL to remember it, but please advise if I misunderstood.

    - u x 1/3 = - u / 3

    No?
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  6. #6
    Super Member Quacky's Avatar
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    Re: Expressions containing fractions and simplifying

    That's right. FOIL is a general approach to quadratics; multiply the:
    First,
    Outside,
    Inside
    Last

    ...terms together. You don't have to use it to expand if you prefer not to. The method you used in the original post is fine except for a very minor error when taking the fraction into account.
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  7. #7
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    Re: Expressions containing fractions and simplifying

    Quote Originally Posted by Quacky View Post
    That's right. FOIL is a general approach to quadratics; multiply the:
    First,
    Outside,
    Inside
    Last

    ...terms together. You don't have to use it to expand if you prefer not to. The method you used in the original post is fine except for a very minor error when taking the fraction into account.
    So I made TWO mistakes then?

    Expression;

    (1 - u)(2u + 1/3) = 2u + 1 - 2u^2 - u/3

    Thank you

    David
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  8. #8
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    Re: Expressions containing fractions and simplifying

    Quote Originally Posted by David Green View Post
    So I made TWO mistakes then?

    Expression;

    (1 - u)(2u + 1/3) = 2u + 1 - 2u^2 - u/3

    Thank you

    David
    The value marked in red is unfortunately wrong because 1 \cdot \frac13 = \frac13.
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