You can do this:
(%i2) float(rectform(solve(((40-3*x)*(20-2*x)*x)/2-500)));
(%o2) [x = 2.220446049250313e-15 %i + 6.234149131052292,
x = 1.740696735598142 - 1.332267629550188e-15 %i,
x = 15.3584874666829 - 4.440892098500626e-16 %i]
Sometimes you have to reverse the order of calling
float() and rectform().
I modified float and wrote chop(), so you can do this:
(%i4) chop(float(solve(((40-3*x)*(20-2*x)*x)/2-500)));
(%o4) [x = 6.234149131052293, x = 1.740696735598141, x = 15.3584874666829]
--John
On 10/13/2013 03:19 PM, Joerg Rauh wrote:
> ("5.28.0-2","2012-08-27 23:16:48","i686-pc-mingw32","GNU Common Lisp
(GCL)","GCL 2.6.8")
>
> Dear Maxima Supporter,
> out of wxMaxima 12.04.0 I had Maxima solve for x:
> ((40-3*x)*(20-2*x)*x)/2-500
> Here are the results:
>
[x=(-(sqrt(3)*%i)/2-1/2)*((250*sqrt(101)*%i)/3^(7/2)+25750/729)^(1/3)+(1300*((sqrt(3)*%i)/2-1/2))/(81*((250*sqrt(101)*%i)/3^(7/2)+25750/729)^(1/3))+70/9,
>
x=((sqrt(3)*%i)/2-1/2)*((250*sqrt(101)*%i)/3^(7/2)+25750/729)^(1/3)+(1300*(-(sqrt(3)*%i)/2-1/2))/(81*((250*sqrt(101)*%i)/3^(7/2)+25750/729)^(1/3))+70/9,
>
x=((250*sqrt(101)*%i)/3^(7/2)+25750/729)^(1/3)+1300/(81*((250*sqrt(101)*%i)/3^(7/2)+25750/729)^(1/3))
>
> It missed the real results: x=1.7407 and x=6.23415, which I found here:
>
http://www.wolframalpha.com/input/?i=solve%28%28%2840-3*x%29%2F2%29*%2820-2*x%29*x-500%2Cx%29
>
> Is there anything I can do differently to make it find the real solutions?
> Thank you and kind regards
>
> Joerg
>
>
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