If I have the cubic equation, how can i find the real root of x ? I try this but i get complex root
Solve[b (q - 1)*(x^3) + (m - s)*(x^2) + (a - n)*x + v == 0, x]
where b,q,m,s,a,n,v are nonnative parameters
I apprciate for help
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1 Answer
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Reduce[b (q - 1)*(x^3) + (m - s)*(x^2) + (a - n)*x + v == 0, x, Reals]
and many many more ...
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1$\begingroup$ So what your answer is supposed to demonstrate? This is not even an explicit form---you have
Rootobject. And why is there so many roots? $\endgroup$– yarchikCommented Jun 27, 2020 at 12:11 -
1$\begingroup$ @yarchik Adding the parameter constraints can help though:
Reduce[Flatten[{b (q - 1)*(x^3) + (m - s)*(x^2) + (a - n)*x + v == 0, Map[# > 0 &, {b, q, m, s, a, n, v}]}], x, Reals]$\endgroup$ Commented Jun 27, 2020 at 16:24
Discriminant[cubic, x] >= 0. $\endgroup$