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Math Help - Variable with exponential equation help

  1. #1
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    Variable with exponential equation help

    Hi there, I seem to be having trouble with this equation. (X^3+5)/4=8

    My idea was to multiply the values inside the bracket by 4 to undo the division, and then to do the same to the RHS...ie. 4x8, and work from there...but this gave me x= 1.4422495

    But this method does not work out. I used my casio Classpad 330 to solve the equation, and x=3

    Can someone give me a heads up where I am going wrong
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  2. #2
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    Re: Variable with exponential equation help

    Hello, Tren301!

    Hi there, I seem to be having trouble with this equation: . \frac{x^3+5}{4}\:=\:8

    My idea was to multiply the values inside the bracket by 4 to undo the division . What?
    and then to do the same to the RHS ... ie, 4x8, and work from there ... but this gave me x= 1.4422495

    But this method does not work out. I used my casio Classpad 330 to solve the equation, and x=3

    Can someone give me a heads up where I am going wrong?

    We are given: . \frac{x^3+5}{4} \:=\:8

    Multiply by 4: . {\color{red}4}\cdot\frac{x^3+5}{4} \:=\:{\color{red}4}\cdot8

    And we have: . x^3 + 5 \:=\:32 \quad\Rightarrow\quad x^3 \:=\:27 \quad\Rightarrow\quad x \:=\:3
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  3. #3
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    Re: Variable with exponential equation help

    \displaystyle \frac{x^3+5}{4}=8

    \displaystyle x^3+5=8\times 4

    \displaystyle x^3+5=32

    \displaystyle x^3=32-5

    \displaystyle x^3=27

    \displaystyle x=\sqrt[3]{27} = 3
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