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Math Help - Ti-83 giving inconsistent answers

  1. #1
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    Ti-83 giving inconsistent answers

    What I have been doing is just taking a fraction and raising it to ^(1/2) to find the difference of squares and it has worked for every problem except this one, and it seems to be a fault with the calculator.
    For instance
    \frac{16}{81}x^4-16=(\frac{4}{9}x^2-4)(\frac{4}{9}x^2+4)=(\frac{2}{3}x-2)(\frac{2}{3}x+2)(\frac{4}{9}x^2+4)

    For some reason in my TI-83 if I just enter \frac{16}{81}^{1/2} it will yield \frac{16}{9}

    but if I do \frac{16}{81} = .1975308642, turn it back into the fraction \frac{16}{81} and then raise that to ^{1/2} it will give me the correct fraction \frac{4}{9}

    Very strange indeed, anyone know why the calculator might be doing this?

    Same thing for \frac{4}{9} if I just try to raise this to ^(1/2) in the calculator it will yield 1.333 repeating, which equals \frac{4}{3} when converted back to a fraction. But if I do \frac{4}{9} it will yield .444 repeating, turn it back into the fraction \frac{4}{9} and then I can raise that to ^(1/2) to get the correct answer which is \frac{2}{3}
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  2. #2
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    Quote Originally Posted by allyourbass2212 View Post
    What I have been doing is just taking the number or fraction and raising it to ^(1/2) to find the difference of squares and it has worked for every problem except this one, and it seems to be a fault with the calculator.
    For instance
    \frac{16}{81}x^4-16=(\frac{4}{9}x^2-4)(\frac{4}{9}x^2+4)=(\frac{2}{3}x-2)(\frac{2}{3}x+2)(\frac{4}{9}x^2+4)

    For some reason in my TI-83 if I just enter \frac{16}{81}^{1/2} it will yield \frac{16}{9}

    but if I do \frac{16}{81} = .1975308642, turn it back into the fraction \frac{16}{81} and then raise that to ^{1/2} it will give me the correct fraction \frac{4}{9}

    Very strange indeed, anyone know why the calculator might be doing this?

    Same thing for \frac{4}{9} if I just try to raise this to ^(1/2) in the calculator it will yield 1.333 repeating, which equals \frac{4}{3} when converted back to a fraction. But if I do \frac{4}{9} it will yield .444 repeating, turn it back into the fraction \frac{4}{9} and then I can raise that to ^(1/2) to get the correct answer which is \frac{2}{3}
    If you type 16/81^(1/2) then only the square-root of 81 will becalculated.

    With a TI83 you better write fractions in brackets. Type (16/81)^(1/2) and afterwards MATH ENTER ENTER
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  3. #3
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    Ah, many thanks Earboth!
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