Use the inverse function theorem to estimate the change in the roots

In summary, the conversation discusses using the inverse function theorem to estimate the change in the roots of a cubic polynomial when the coefficients are changed by a small amount. The inverse function theorem can be used by filling in the first root $x_1$ and taking the derivative with respect to it. The change in the coefficients is represented by $\Delta a$, which in this case is equal to 0.01 times the original coefficients.
  • #1
i_a_n
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Let $p(\lambda )=\lambda^3+a_2\lambda^2+a_1\lambda+a_0=(\lambda-x_1)(\lambda-x_2)(\lambda-x_3)$ be a cubic polynomial in 1 variable $\lambda$. Use the inverse function theorem to estimate the change in the roots $0<x_1<x_2<x_3$ if $a=(a_2,a_1,a_0)=(-6,11,-6)$ and $a$ changes by $\Delta a=0.01a$. How can I use the inverse function theorem to estimate?
 
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  • #2
ianchenmu said:
Let $p(\lambda )=\lambda^3+a_2\lambda^2+a_1\lambda+a_0=(\lambda-x_1)(\lambda-x_2)(\lambda-x_3)$ be a cubic polynomial in 1 variable $\lambda$. Use the inverse function theorem to estimate the change in the roots $0<x_1<x_2<x_3$ if $a=(a_2,a_1,a_0)=(-6,11,-6)$ and $a$ changes by $\Delta a=0.01a$. How can I use the inverse function theorem to estimate?

You could start by filling in $x_1$ in $p(\lambda )=\lambda^3+a_2\lambda^2+a_1\lambda+a_0=0$ and taking the (total) derivative with respect to $x_1$.
 
  • #3
I like Serena said:
You could start by filling in $x_1$ in $p(\lambda )=\lambda^3+a_2\lambda^2+a_1\lambda+a_0=0$ and taking the (total) derivative with respect to $x_1$.

What $\Delta a$ means? Can you give me a more complete answer? Thank you.

Who can provide me a complete answer?
 
Last edited:

Related to Use the inverse function theorem to estimate the change in the roots

1. What is the inverse function theorem?

The inverse function theorem is a mathematical theorem that states that if a function has a continuous and non-zero derivative at a point, then it has a local inverse function at that point.

2. How does the inverse function theorem relate to estimating the change in roots?

The inverse function theorem can be used to estimate the change in roots of a function by considering the behavior of the derivative at a specific point. This allows us to make predictions about the behavior of the function and its roots in a local neighborhood of that point.

3. Can the inverse function theorem be applied to all types of functions?

No, the inverse function theorem can only be applied to functions that have a continuous and non-zero derivative at a specific point. If a function does not meet these criteria, the theorem cannot be used to estimate the change in roots.

4. What is the benefit of using the inverse function theorem to estimate the change in roots?

Using the inverse function theorem allows us to make local predictions about the behavior of a function and its roots, which can be useful in solving problems and making decisions in various scientific fields.

5. Are there any limitations to using the inverse function theorem for estimating the change in roots?

Yes, there are limitations to using the inverse function theorem. It can only provide an estimate of the change in roots, and the actual behavior of the function may differ from the predicted behavior. Additionally, the theorem may not be applicable to all types of functions, as mentioned in the answer to question 3.

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