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Really hope someone can help me! I've been struggling with this issue the past 5 hours and can't seem to figure out why or simply don't understand the outcome.

I'm solving a cubic equation using the "depressed equation" method and then cardanos' formula. If I solve the cubic equation in my CAS (TI-Inspire) I get one result, but if I solve the depressed equation via cardanos' method, I get a different result. Isn't those two results suppose to be the same (finding the root)?

I get a complex number as the result, but I think I'm suppose to get the real number solution. Am I doing something wrong here?

Thanks in advance Mike

image over calculations

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    can you give us the complete formulas you used? – 2017-02-14
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    All cubics have 3 solutions: 1 real and 2 complex (non-real) solutions, or all 3 solutions are real. I'm guessing the CAS is only showing you one of the 3 possible roots, and your two different inputs are producing 2 different roots (of the 3 possible) to show you as output. I suggest modifying your input to the CAS to show all three solutions in both cases. – 2017-02-14
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    http://i.imgur.com/UktNjJc.png I used the Cardanos' formula for depressed equation :) – 2017-02-14
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    A bit unsure, but the Cardanos' formula is only for when p & q in the depressed equation are of positive numbers? If so, how do I handle the negative P value I have? (-3.25) – 2017-02-14

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