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Math Help - evaluate expressions with sets

  1. #1
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    evaluate expressions with sets

    Im stuck on this 2 problems.. help plz!

    1.) P = {x E N/x^2 -9=0}

    2.) F = {x E Q / (3x-4)(x-√2)=0}

    Thank you! I'll appreciate it
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  2. #2
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    Quote Originally Posted by ruben22 View Post
    Im stuck on this 2 problems.. help plz!

    1.) P = {x E N/x^2 -9=0}

    2.) F = {x E Q / (3x-4)(x-√2)=0}

    Thank you! I'll appreciate it
    1. Solve the given equations.

    2. Afterwards check if the solutions belong to the given domain.

    3. An example:

    L=\{y \in \mathbb{N}|(2y-5)(y-\sqrt{3})(y^2-1)=0\}

    A product equals zero if one of the factors equals zero:

    \begin{array}{ccc}2y-5=0&y-\sqrt{3}=0&y^2-1=0 \\<br />
y=\frac52&y=\sqrt{3}&y=1\vee y=-1 \end{array}

    As you easily can see only y = 1 is a valid solution. Thus

    L=\{1\}
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  3. #3
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    That's my problem...I don't know how to use this theory on the problems i was given. I'm not that good at mad :-s
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