Can you have a formula for every degree of polynomial?

Click For Summary

Discussion Overview

The discussion revolves around the existence of formulas for solving polynomial equations of various degrees, particularly focusing on the implications of the Abel-Ruffini theorem regarding polynomials of degree five and higher. Participants explore whether it is possible to generalize solutions for all polynomial degrees or if individual formulas can be constructed for specific cases.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that there is no general formula for polynomials of degree five or higher due to the Abel-Ruffini theorem.
  • Others question whether it is possible to create a formula for individual higher-degree polynomials by breaking them down into simpler components, such as quadratic equations.
  • Concerns are raised about solving higher-degree polynomials that cannot be factored, with references to the limitations imposed by the Abel-Ruffini theorem.
  • Participants discuss the nature of potential formulas for higher-degree polynomials, noting that while formulas may exist, they cannot be expressed using only elementary algebraic operations.
  • There is mention of numerical methods that can provide approximate solutions to polynomial equations, though the reasons for the lack of exact solutions for certain cases are debated.
  • One participant expresses confusion regarding the relationship between input values and the inability to derive exact solutions for higher-degree polynomials.
  • Another participant clarifies that while there can be formulas for roots of higher-degree polynomials, these may not involve radicals and that no single formula exists for all degrees.

Areas of Agreement / Disagreement

Participants generally disagree on the possibility of having a general formula for all polynomial degrees, with some asserting that such formulas do not exist beyond degree four, while others explore the potential for individual solutions. The discussion remains unresolved regarding the implications of the Abel-Ruffini theorem and the nature of solutions for higher-degree polynomials.

Contextual Notes

Participants express uncertainty about the specific limitations of the Abel-Ruffini theorem and the conditions under which higher-degree polynomial solutions can be expressed. There is also a lack of consensus on the methods available for solving these equations and the nature of the solutions.

questionpost
Messages
194
Reaction score
0
I have some math people who say you can, and some who say you can't beyond quintic because of the Abel-Ruffini theorem. Which is it? Can I generalize all polynomials? Or at least can I manually make a formula for each individual degree?
 
Physics news on Phys.org
There is no general formula for polynomials of degree five or higher.
 
Jorriss said:
There is no general formula for polynomials of degree five or higher.

So even if I have it set to 0, there's no possible way to get a single formula for a hex-tic polynomial? What if I write it in the formula to break it down into 3 different quadratic equations?
 
questionpost said:
So even if I have it set to 0, there's no possible way to get a single formula for a hex-tic polynomial? What if I write it in the formula to break it down into 3 different quadratic equations?
Of course you can come up with examples of polynomials that are easily factorizable, but there is no general formula for, say, ax^6 + bx^5 + cx^4 + dx^3 + fx^2 + gx^1 + h = 0.
 
Jorriss said:
Of course you can come up with examples of polynomials that are easily factorizable, but there is no general formula for, say, ax^6 + bx^5 + cx^4 + dx^3 + fx^2 + gx^1 + h = 0.

Well how am I suppose to solve a higher degree polynomial that I can't factor? Also, I know the abel-ruffini theorem exists, but I don't get exactly why it says you can't have formulas bigger than 5th degree.
 
questionpost said:
Well how am I suppose to solve a higher degree polynomial that I can't factor? Also, I know the abel-ruffini theorem exists, but I don't get exactly why it says you can't have formulas bigger than 5th degree.
You can have formulas, but those formulas would not be expressible in terms of elementary algebraic operations, specifically addition, subtraction, multiplication, division, and taking roots.
 
lugita15 said:
You can have formulas, but those formulas would not be expressible in terms of elementary algebraic operations, specifically addition, subtraction, multiplication, division, and taking roots.

What would they be expressible in then?
 
questionpost said:
Well how am I suppose to solve a higher degree polynomial that I can't factor?
There are a number of numerical methods that can give approximate solutions to polynomial equations.
questionpost said:
Also, I know the abel-ruffini theorem exists, but I don't get exactly why it says you can't have formulas bigger than 5th degree.
 
Mark44 said:
There are a number of numerical methods that can give approximate solutions to polynomial equations.

Why not an exact answer? If there's a specific process being done to the input, how is there not a specific answer? That doesn't even make sense. You don't type in y or z ≈x, you type in y or z = x. What about logs? that's not a subtraction or addition or multiplication or division or root, what about exponents? or vectors?
I just don't get how I could input a number in x^7+3x^3-12 and get an exact answer but if I work backwards I somehow don't get that exact input I started with.
 
  • #10
The point of Abel-Ruffini is that, for n greater than 4, there exist polynomials of degree n having zeroes that cannot be written in terms of radicals. There can exist formulas for roots of such polynomials that do not use radicals. I believe, but am not certain, that there is no one formula for all n.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 0 ·
Replies
0
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
9
Views
4K
  • · Replies 3 ·
Replies
3
Views
3K