Roots of polynomial equations ( Substitution )

In summary, to reduce u^4 + 5u^3 + 6u^2 + 5u + 1 = 0 to v^2 + 5v + 4 = 0 using v = u + 1/u, you can either divide through by u^2 or substitute v into the equation. This method can also be used to solve other equations such as x^6-6x^5+14x^4-18x^3+14x^2-6x+1=0 or x^6-9x^5+29x^4-42x^3+29x^2-9x+1=0.
  • #1
Erfan1
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0
How do I reduce u^4 + 5u^3 + 6u^2 + 5u + 1 = 0 to v^2 + 5v + 4 = 0 by using v = u + 1/u ?
 
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  • #2
Erfan said:
How do I reduce u^4 + 5u^3 + 6u^2 + 5u + 1 = 0 to v^2 + 5v + 4 = 0 by using v = u + 1/u ?

Since \(\displaystyle u \ne 0\) you may divide through by \(\displaystyle u^2\).

What do you notice now?
 
  • #3
Erfan said:
How do I reduce u^4 + 5u^3 + 6u^2 + 5u + 1 = 0 to v^2 + 5v + 4 = 0 by using v = u + 1/u ?
You can do as M R suggested or you can put $v=u+1/u$ in $v^2+5v+4=0$. You should get $u^4 + 5u^3 + 6u^2 + 5u + 1 = 0$.
 
  • #4
You can use the same idea to solve \(\displaystyle x^6-6x^5+14x^4-18x^3+14x^2-6x+1=0\), which I made specially for you. :)
 
  • #5
And a slightly nicer one \(\displaystyle x^6-9x^5+29x^4-42x^3+29x^2-9x+1=0\).
 

FAQ: Roots of polynomial equations ( Substitution )

What are the roots of a polynomial equation?

The roots of a polynomial equation are the values of the variable that make the equation equal to zero. In other words, they are the solutions to the equation.

How do you find the roots of a polynomial equation?

One way to find the roots of a polynomial equation is by using substitution. This involves replacing the variable in the equation with a value and solving for the resulting expression to equal zero. This process is repeated for each root of the equation.

What is the importance of finding the roots of a polynomial equation?

Finding the roots of a polynomial equation can help in understanding the behavior of the equation and its graph. It also allows for solving real-world problems that involve finding the values of a variable.

Can all polynomial equations be solved using substitution?

No, not all polynomial equations can be solved using substitution. Some equations may have irrational or complex roots that cannot be found using substitution alone. In these cases, other methods such as factoring or using the quadratic formula may be necessary.

How do the number of roots relate to the degree of a polynomial equation?

The fundamental theorem of algebra states that a polynomial equation of degree n will have n roots, including complex roots. This means that the number of roots is equal to the degree of the polynomial equation.

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