How do you find all the real and complex roots of #x^7 – x^5 + x^2 – 3x + 3 = 0#?

Question

1480 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-07-22T06:32:13

Use a numerical method to find approximations:

#x ~~ -1.50525#

#x ~~ 0.443441+-0.934112i#

#x ~~ -0.740689 +- 1.01346i#

#x ~~ 1.04988+-0.284124i#

In common with most polynomials of degree #5# or greater, this septic equation has no solutions expressible using #n#th roots.

About the best we can do is find numerical approximations to the roots using a method like Durand-Kerner.

See an example for a quintic, describing the method at: https://socratic.org/s/awnFhaqT

Here's an example C++ program that implements the method for this septic:

enter image source here

Using this program I found the following approximations:

#x ~~ -1.50525#

#x ~~ 0.443441+-0.934112i#

#x ~~ -0.740689 +- 1.01346i#

#x ~~ 1.04988+-0.284124i#