Create a function that will output the three roots of a cubic equation specified by the 4 coefficients listed as input. The output should be sorted using the "sort" function of matlab, to be consistent. Also, the output need only be accurate to the 4th decimal place, and the input "A" will always be non-zero and real.
Example:
A*x^3+B*x^2+C*x+D=0 --> [A,B,C,D]
x^3-6x^2+11x-6=0 --> [1,-6,11,-6]
cubicFormula([1,-6,11,-6]) --> [1,2,3]
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the "sorted" requirement is problematic, I would suggest you drop this requirement and simply resort the output of cubicFormula after (not before) rounding to four digits (and apply the same logic to your testsuite)...
is there maybe a several problem with the sorting method you describe/need?? :-/
The problem requires abs as 'ComparisonMethod' for sorting and the non-conjugate transpose. That's a pain that I have just become aware: ' is the conjugate transpose, and .' is the non-conjugate transpose. The conjugate operator changes the signs of complex roots.