Find roots



This challenge might be interesting to some people.  Try to find the three 
real roots to log(x^3-x*78+90)+x.  I had a hard time with it.

-----Original Message----- 
From: Raymond Toy
Sent: Thursday, January 03, 2013 6:31 PM
To: maxima at math.utexas.edu
Subject: Re: [Maxima] Find roots

>>>>> "Jo?o" == Jo?o Vieira Gomes <vieiragomes at sapo.pt> writes:

    Jo?o> How can we use Maxima to find the real roots of equation 
log(x^2)+%e^x+3=-x?

    Jo?o> Solve just give x=-2*log(x)-%e^x-3.

If you want a numerical answer, you can use find_root:

find_root(log(x^2)+%e^x+3=-x, x, 0.1, 1) -> .1196296556538211

I found the limits by plotting the function log(x^2)+%e^x+3+x and
noticing that there is a root near 0.1.  Since this function is
monotonic for x > 0, it's also the only root.  I leave it as an
exercise to find the other real root.

Ray

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