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I am using Maple to find the roots of a non-linear equation in one variable. When I solve the equation, I get only 2 negative roots whereas if I plot the graph of the function, it also shows that the graph cuts the positive x-axis at least once,

I have attached the graph and the code as an image.

enter image description here

What do I do to get that positive root?

P.S. I did the same thing on MATLAB too, but the program gave me the same negative roots.

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  • $\begingroup$ Try 'fsolve(f(x)=0,x=guess)' where 'guess' is some positive first guess for the solution for example guess=$5\cdot 10^8$ $\endgroup$
    – Winther
    Nov 28, 2014 at 6:43
  • $\begingroup$ @Winther It doesn't work for me. Did you try it? If it is working for you, then I am probably using an older version of Matlab. $\endgroup$ Nov 28, 2014 at 6:51
  • $\begingroup$ That was code for maple $\endgroup$
    – Winther
    Nov 28, 2014 at 6:53
  • $\begingroup$ Could you put your equation in a readable form, please ? I am almost blind and I can't get it. Thanks. $\endgroup$ Nov 28, 2014 at 7:08
  • $\begingroup$ @Winther Thanks, I got it. $\endgroup$ Nov 28, 2014 at 7:26

1 Answer 1

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Using Maple,

restart:

ee:=-1410+2.518380702e-8*H
    +0.00000909090909*H*(arcsinh(8.04024700e7/H)
                         +arcsinh(7.750000000e7/H)):

#plot(ee,H=-10^9..10^9);

solve(ee);

                                8                 8
                 -9.455498998 10 , -2.796395661 10 

fsolve(ee,H=0..infinity);

                                         8
                           2.135901827 10 

Student:-Calculus1:-Roots(ee, -10^9..10^9);

        [               8                 8                8]
        [-9.455498998 10 , -2.796395661 10 , 2.135901827 10 ]
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