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Math Help - Multiplicative Inverse?

  1. #1
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    Multiplicative Inverse?

    Solve 3/4x - 5 = 4

    What I don't understand, is if I have to multiply each side by the reciprocal how do I do it if the reciprocal is infinite like 3/4, which ends up being 1.3333333 etc. etc.
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  2. #2
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    \begin{array}{rcl}<br />
 \frac{3}{4}x - 5 & = & 4 \\ <br />
 \frac{3}{4}x & = & 9 \\ <br />
 \left( {\frac{4}{3}} \right)\frac{3}{4}x & = & 9\left( {\frac{4}{3}} \right) \\ <br />
 x & = & 12 \\ <br />
 \end{array}
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  3. #3
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    to obtain a reciprical, just switch the numerator and denominator.

    the reciprical of 3/4 is 4/3


    * the purpose of a reciprical is to get rid of any coefficients in front of your variable

    so if you have 3/4 x -5 = 4

    first you add 5 to both sides to get:

    3/4 x = 9

    now multiple by the reciprical of 3/4 which is 4/3

    x = 12





    try some practice problems...

    find the reciprical of

    1/12

    34/2

    0.5

    0.1

    NOTE: to find the recipricals of decimals you will first need to find its fractional equivalent.

    the example you provided:

    1.333333333333

    its fraction is 4/3.

    now swithc numerator and denominator to get 3/4
    Last edited by DINOCALC09; December 27th 2007 at 11:19 AM. Reason: typo
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  4. #4
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    Quote Originally Posted by Plato View Post
    \begin{array}{rcl}<br />
 \frac{3}{4}x - 5 & = & 4 \\ <br />
 \frac{3}{4}x & = & 9 \\ <br />
 \left( {\frac{4}{3}} \right)\frac{3}{4}x & = & 9\left( {\frac{4}{3}} \right) \\ <br />
 x & = & 12 \\ <br />
 \end{array}
    Thank you very much both of you for your help, it makes sense now.
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