Finding Roots of an Equation in MATLAB

[adnan jahan]

Dear Fellow,

I need to find the roots of equation
x^8- 2x^6+3x^4-7x^2+a=0
in MATLAB, in such a way that I need 4 non repeating roots.

I have used the technique of
p=[1 -2 3 -7 1]
s=roots(p)
x1=s(1)
x2=s(2)
x3=s(3)
x4=s(4)
where xi,i=1,2,3,4 are roots of the above equation,

2nd option my friend gave me is

p=[1 -2 3 -7 1]
s=sqrt(roots(p))
x1=s(1)
x2=s(2)
x3=s(3)
x4=s(4)
this will again give me four roots of the equation,

need your help to find the four roots of above equation.


Regards

 

[uart]

Clearly your polynomial is in x^2, so your friends solution is the correct one. Though you should of course use the plus and minus (+/-) of the roots.

 

[adnan jahan]

Okay ,,,, thanks uart,, that's really help full

 

[adnan jahan]

can you please give my any idea how to define vertical axis in MATLAB plot command

thanks

 

[Pythagorean]

can you please give my any idea how to define vertical axis in MATLAB plot command

thanks

it's automatically designated by your data set, but you can also set particular properties of the axis with (for example):

set(gca,'YTick',[0 0.05 0.075 0.1 0.15 0.2 0.25])

and you could even go as far as to label each of the points:

set(gca,'YTickLabel','0|0.05|Cutoff|0.1|0.15|0.2|0.25')

full documentation:
http://www.mathworks.com/help/techdoc/creating_plots/f1-19798.html