Re: cubic roots



Eric wrote:

I am currently working on a problem where I need to
find some cubic roots but am having some trouble.
Can anyone hint me towards getting the answer. The
e problem is:
x^3 + (a^2+b^2+c^2)*x - c^2 = 0, where a,b,c have
any value.

For another problem, the question says to prove
that if you have a matrix that is block diagonal [a 0
; 0 b] show that the e-values of a and b are the
e-values of the overall matrix. I understand this
concept, but don't quite know where to start to prove
this.

if x=r is a solution of x^3 + (a^2+b^2+c^2)*x - c^2 =
0 then
so is x = 1/2/r*(-r^2+(r^4-4*r*c^2)^(1/2)) and x =
1/2/r*(-r^2-(r^4-4*r*c^2)^(1/2))

Chris

What did you do to get that equation where x=1/2/r...
.