Factorization for x^3 - 4x^2 -x = 0

In summary, the conversation discusses finding the roots of the equation x^3 - 4x^2 - x = 0 and the eigenvalues of a given matrix. The speaker initially thought 1 was a root, but upon further calculation, realized it was not. They were able to find one of the roots by dividing the equation by (x-1) and then solving for the remaining roots using the quadratic formula. The conversation also mentions an eigenvector of the given matrix.
  • #1
teng125
416
0
for x^3 - 4x^2 -x = 0 , i have found one of the root which is 1 by dividing this equation by (x-1).
from there onwards i can't do already to find the other two roots.somebody pls help

thanx
 
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  • #2
1 is not a root, 0 is. Unless you have posted the wrong equation.
 
  • #3
sorry.the matrix is [1 2 1;2 1 1;1 1 2].so i want to find the eigenvalues
 
  • #4
therefore i got the eqn x^3 - 4x^2 -x = 0
 
  • #5
fine, but 1 is still not a root (1-4-1 is not zero)
 
  • #6
The characteristic equation for the matrix you give is x^3- 4x^2- x+ 4=0
not what you give. That equation does have 1 as a root so apparently you just wrote the equation wrong (twice!).
You say you found that 1 was a root "by dividing this equation by (x-1)" (Which makes me wonder why you chose x-1. It's simpler just to set x= 1 in the equation!). When you did that surely you found that
x^3- 4x^2- x+ 4= (x-1)(x^2- 3x- 4). Solve x^2- 3x- 4= 0. That factors easily but even it it didn't you could use the quadratic formula.
 
  • #7
If you find the quadratic formula eerie, recognize that (1,1,1) is an eigenvector of your matrix.
 
  • #8
oooo...okok thanks very much
 

1. What is factorization for x^3 - 4x^2 -x = 0?

Factorization is the process of breaking down a mathematical expression into smaller parts, known as factors. In this case, we are trying to find the factors of the polynomial x^3 - 4x^2 - x, which means finding the numbers or expressions that can be multiplied together to give us the original polynomial.

2. Why is factorization important in mathematics?

Factorization is important in mathematics because it allows us to simplify complex expressions, solve equations, and find the roots of polynomials. It also helps in understanding the relationships between different mathematical concepts and allows us to make connections between them.

3. How do you factorize x^3 - 4x^2 - x = 0?

To factorize x^3 - 4x^2 - x = 0, we can use the method of grouping, where we group the terms with common factors together and then factor out the common factor. In this case, we can factor out an x from the expression, giving us x(x^2 - 4x - 1) = 0. Then, we can factor the quadratic expression inside the parentheses as (x - 1)(x + 1), giving us the final factorization of x(x - 1)(x + 1) = 0.

4. Can we use the quadratic formula to factorize x^3 - 4x^2 - x = 0?

No, the quadratic formula can only be used to find the roots of a quadratic equation, which has the form ax^2 + bx + c = 0. In this case, we have a cubic equation, and the quadratic formula cannot be applied. We need to use other methods, such as grouping or factoring by grouping, to factorize the polynomial.

5. What are the solutions to x^3 - 4x^2 - x = 0?

The solutions, or roots, of x^3 - 4x^2 - x = 0 can be found by setting each factor equal to zero and solving for x. This gives us x = 0, x = 1, and x = -1 as the three solutions to the equation. We can also verify these solutions by plugging them back into the original equation and seeing if they make the equation true. In this case, all three solutions satisfy the equation, making them the correct solutions.

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