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Thread: subbing in x = (u+v)

  1. #1
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    subbing in x = (u+v)

    came across this problem

    $\displaystyle x^3+px=q$

    sub in $\displaystyle x=u+v$

    then it says they got this

    $\displaystyle u^3+v^3+(3uv+p)(u+v) = q$ how did it become this? $\displaystyle x^3 \Rightarrow u^3+v^3$ this makes sense but the $\displaystyle (3uv+p)(u+v)$ doesn't. why isn't it just $\displaystyle p(u+v)$
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  2. #2
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    Re: subbing in x = (u+v)

    ...

    expand out $(u+v)^3$
    Thanks from Jonroberts74
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  3. #3
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    Re: subbing in x = (u+v)

    oh geez. maybe reading math this late at night is a bad idea. haha
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