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5-Regular Member
March 16, 2026
Question

Problem with basic calculations

  • March 16, 2026
  • 2 replies
  • 347 views
mathcad cannot handle correctly the swap of negative symbol in odd powers.
Specific, calculating this expression (-1/8)^(-2/3) gives an imaginary result instead of the 4 as result

    2 replies

    21-Topaz II
    March 16, 2026

    Prime gets this:

    Capture.JPG

    Maple Flow gets this:

    Capture2.JPG

    Matlab gets this:

    Capture3.JPG

    Julia:

    Capture4.jpg

    Cheers

    Terry

    21-Topaz II
    March 16, 2026

     

    Octave:

    Capture5.JPG

    Wolfram:

    Capture6.JPG

    Python:

    Capture7.JPG

    5-Regular Member
    March 16, 2026

    The original solution as presented in the book MODERN ENGINEERING MATHEMATICS
    Glyn James, Phil **bleep**, Sixth Edition

    page 7

    is as shown in screenshot. Its just a simple and direct solution on this.

     

    Screenshot 2026-03-16 152720.png

    21-Topaz II
    March 16, 2026

    Hi,

    Both answers are correct:

    Capture8.JPG

    21-Topaz II
    March 17, 2026

    Thanks for spotting this, remember 7 mathematical programs get the complex result.

    You can with some manipulation of the problem get 4.

    The first step in the solution from the book gets 4.

    Capture.JPG

    It seems cube root gets 4 raising to the 1/3 power gets the complex result.

    Capture2.JPG

    Very interesting learning thank you for spotting this.

    Cheers

    Terry