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Plotting a Graph with Fraction Exponent

Posted 11 years ago
Hello,

I have a TI-89 Titanium Calculator .... I plotted the equation x^(4/3) + 4*x^(1/3) and it was presented nicely by the calculator.  I try to plot it using Mathematica 9.0...but to my surprise it didn't produce the curve when x < 0.  Just wondering if the TI calculator is displaying a wrong curve at x<0...my question how can i duplicate the curve produce by the calculator using Mathematica at x<0.

Bobby
POSTED BY: Bobby Catahan
2 Replies
For negative values, x^(1/3) can have 3 different values.  The default meaning of x^(1/3) is not to take the real value. To see this evaluateN[(-1)^(1/3)]. The default value is the first root counter clockwise from the real positive axis. There's a method a method and reason to this - it provides a consistent interpretation for what the nth root of a negative number returns. 

There is a function which returns the Real value of the root. It's called Surd:

Plot[Surd[x, 3]^4 + 4*Surd[x, 3], {x, -5, 5}]
POSTED BY: Sean Clarke
Posted 11 years ago
Sean,

Highly Appreciate you quick response the the question...Just plotted the equation using the syntax you gave and it was the same as the TI calculator...Thank  and will study the Surd option of Mathematica...

Regards,

Bobby
POSTED BY: Bobby Catahan
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