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Thread: Adding a fraction to a whole number in an algebraic equation

  1. #1
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    Adding a fraction to a whole number in an algebraic equation

    Hello!

    I am going over another answer for a question on an online test:
    Adding a fraction to a whole number in an algebraic equation-algebra.png
    The only question I have is, how did they get 9/2? The way I'd go about solving this is making the -4 a -4/1, and then adding -1/2 to get 4/2. Where am I going wrong?

    Thanks in advanced!
    -Neo
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    Re: Adding a fraction to a whole number in an algebraic equation

    $\displaystyle \begin{align*} -\frac{1}{2} - 4 &= - \left( \frac{1}{2} + 4 \right) \\ &= - \left( \frac{1}{2} + \frac{8}{2} \right) \\ &= -\frac{9}{2} \end{align*}$
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    Re: Adding a fraction to a whole number in an algebraic equation

    I'm sorry, I still don't get it... I know that -1/2 + 4 = -(1/2 + 4), but to get 8/2, did you multiply 4/1 by 2? And if so, why? Is it because 2 is the denominator?

    Thank you for your efforts! ^^
    -Neo
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    Re: Adding a fraction to a whole number in an algebraic equation

    Quote Originally Posted by SpaghettNeo View Post
    I know that -1/2 + 4 = -(1/2 + 4)....
    No. -1/2 + 4 = -(1/2 - 4)
    That's really -1(1/2 - 4)
    So: -1*(1/2) = -1/2, -1*(-4) = +4
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    Re: Adding a fraction to a whole number in an algebraic equation

    Quote Originally Posted by SpaghettNeo View Post
    I'm sorry, I still don't get it... I know that -1/2 + 4 = -(1/2 + 4), but to get 8/2, did you multiply 4/1 by 2? And if so, why? Is it because 2 is the denominator?
    First: $\large{ - \frac{1}{2} + 4 \ne - \left( {\frac{1}{2} + 4} \right)}$

    Can you do this $\dfrac{8}{2} - \dfrac{1}{2}~?$
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