Solving 2 degree polynomial

Can anyone please help me with this
mu = 0.15; SW = 9.5106e+03; Cldeck = -1.8001; gammaw = 9.81; mu1 = 1.3; L=40; W = 12.5; mu2 = 12; sigma1 = 0.5; sigma2 = 1; hb = 10; gd = 1.1; n = 4; gw = 0.388; Z1 = 0.7602*x; Z2 = 0.6497*x
GZ = (mu*(SW-((0.5*Cldeck*gammaw*(mu1+Z1*sigma1).^2*L*W) + (gammaw*(L*((mu2+Z2*sigma2)-hb-gd)*W + (L*gd*gw*n))))))==0;
beta = round(solve(GZ,x),4)
- 0.922 - 4.2175i
- 0.922 + 4.2175i
I am getting imaginary roots for this equation but actually solving this by calculator leads to real roots why so?
actual roots are
-0.922
-0.922

4 Comments

Verify your equation, GZ is correct. If you simplifiy(GZ), I get:
23937561971005804986039*x^2 +44140442005713908921200*x+1338370076196338394974528/3==0
Solving the above gives the matlab solution.
Hello david Thanks for your prompt reply.
Can you please tell me how you get the above equation from GZ?
Raj Arora
Raj Arora on 12 Apr 2021
Edited: Raj Arora on 12 Apr 2021
on simplify I am getting this
GZ = (93197176391394825*(0.3801*x+ 13/10)^2)/140737488355328 - 478.016775*x + 5703118778359873761/8589934592000000 == 0
and the roots of this equation is again imaginary
23937561971005804986039*x^2 +44140442005713908921200*x+1338370076196338394974528/3==0 same for this
syms x;
mu = 0.15; SW = 9.5106e+03; Cldeck = -1.8001; gammaw = 9.81; mu1 = 1.3; L=40; W = 12.5;
mu2 = 12; sigma1 = 0.5; sigma2 = 1; hb = 10; gd = 1.1; n = 4; gw = 0.388;
Z1 = 0.7602*x; Z2 = 0.6497*x;
GZ = (mu*(SW-((0.5*Cldeck*gammaw*(mu1+Z1*sigma1).^2*L*W) +...
(gammaw*(L*((mu2+Z2*sigma2)-hb-gd)*W + (L*gd*gw*n))))))==0;
simplify(GZ)

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on 12 Apr 2021

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on 12 Apr 2021

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