Posts: 253

Threads: 20

Joined: Jun 2012

Hmmm, that is strange. Hope someone figures it out. HP 50G gives same answer either way (the answer you have second).

Posts: 109

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Joined: Dec 2012

Odd...I got the same result (top screen) on both Home and CAS regardless of maximum or none for auto simplification. The 2 results are correct...how does one get the simplified result for the 1st case?

Posts: 24

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Joined: Sep 2011

Quite interesting, but if you use the Sto command and store both expressions into F1 and F2 for plotting, both show the second answer 2/(6x-3). So presumably only the second answer is correct?

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Joined: Sep 2013

I believe that for the HP Prime the nth root symbol (n odd) of a real number x and the power x^(1/n) are different things. The power x^(1/n) is computed as exp((1/n) LN(x)). If x is negative, then the HP Prime computes LN(x) as the complex number LN(|x|)+ i*pi (principal determination of the logarithm). For the nth root symbol of x, the HP Prime returns x^(1/n) if x is positive and -|x|^(1/n) is x is negative. So the results differ by the multiplicative constant exp(i*pi/n). This should not be a difference for the computation shown because taking LN makes the difference into an additive constant which then should disappear when taking the derivative. I suspect that the HP prime uses different algorithms to simplify each expression.

By the way, the HP50g interprets the nth root of x and the power x^(1/n) the same way, as exp((1/n) LN(x)) with LN(x)=LN(|x|)+i*pi if x is negative.