Saturday, 5 October 2013

real analysis - Simplifying fractional exponents




I am very confused about the following:





whenever I put in into wolfram alpha the answer it gives me is "indeterminate", is it not possible to simplify fractional exponents or something? if the exponent is 2/6 can i simplify it to 1/3 and get -1 as the answer? Provided I'm working with real numbers.



What I put in wolfram alpha was "(-1)^(1/3) real numbers" to which it answered "-1", then when I tried "(-1)^(2/6) real numbers" it answered "indeterminate".


Answer



I figured it out, apparently wolfram first takes the 6th root of -1 and since (-1)^(1/6) is indeterminate since we're dealing with real numbers and can't take an even root of a negative number, it says "indeterminate".




Also, Rory's first solution is absolutely wrong (unless he corrects if when you see this), because we can't take a root of a real negative number raised to a power greater than 1, if what he wrote were true I can then prove that -1 = 1 like so: -1 = (-1)^(1/3) = (-1)^(2/6) = (1)^(1/6) = 1.


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