Writing the Equation for the Polynomial Function

Oct 13, 2025 by wbrum.org 7 views

Introduction

In mathematics, polynomial functions are a fundamental concept in algebra, and understanding their roots is crucial for solving various mathematical problems. When dealing with polynomial functions, we often encounter real roots, but what happens when we have complex roots? In this article, we will explore the concept of complex roots of polynomial functions and how to write the equation for a given set of roots.

What are Complex Roots?

Complex roots are roots of a polynomial function that are not real numbers. They are typically denoted by complex numbers, which are numbers that can be expressed in the form a + bi, where a and b are real numbers, and i is the imaginary unit, which satisfies the equation i^2 = -1. Complex roots can be either purely imaginary or come in conjugate pairs.

The Given Roots

We are given two roots of the polynomial function: 2 + i and 5. Since 5 is a real number, it is a root of the polynomial function. However, 2 + i is a complex root, and we need to find the equation for this polynomial function.

Writing the Equation for the Polynomial Function

To write the equation for the polynomial function, we need to find the other roots of the function. Since the roots of a polynomial function are symmetric with respect to the real axis, we can find the other roots by taking the conjugate of the given complex root.

The Conjugate Root Theorem

The conjugate root theorem states that if a polynomial function has a complex root, then its conjugate is also a root of the function. In this case, the conjugate of 2 + i is 2 - i.

The Other Root

Since the roots of the polynomial function are symmetric with respect to the real axis, we can find the other root by taking the negative of the imaginary part of the given complex root. In this case, the other root is 2 - i.

The Equation for the Polynomial Function

Now that we have found the other root, we can write the equation for the polynomial function. The equation for the polynomial function is given by:

(x - 2 - i)(x - 2 + i)(x - 5) = 0

Simplifying the Equation

We can simplify the equation by multiplying the factors:

(x^2 - 4x + 5)(x - 5) = 0

Expanding the product, we get:

x^3 - 9x^2 + 25x - 25 = 0

Conclusion

In this article, we have explored the concept of complex roots of polynomial functions and how to write the equation for a given set of roots. We have used the conjugate root theorem to find the other root of the polynomial function and have written the equation for the function. The equation for the polynomial function is x^3 - 9x^2 + 25x - 25 = 0.

Frequently Asked Questions

What is the conjugate root theorem? The conjugate root theorem states that if a polynomial function has a complex root, then its conjugate is also a root of the function.
How do I find the other root of a polynomial function? To find the other root of a polynomial function, you can take the negative of the imaginary part of the given complex root.
What is the equation for the polynomial function? The equation for the polynomial function is given by (x - 2 - i)(x - 2 + i)(x - 5) = 0.

References

[1] "Complex Numbers" by Math Open Reference
[2] "Polynomial Functions" by Khan Academy
[3] "Algebra" by MIT OpenCourseWare

Introduction

In our previous article, we explored the concept of complex roots of polynomial functions and how to write the equation for a given set of roots. In this article, we will answer some frequently asked questions about complex roots of polynomial functions.

Q&A

Q: What is the conjugate root theorem?

A: The conjugate root theorem states that if a polynomial function has a complex root, then its conjugate is also a root of the function.

Q: How do I find the other root of a polynomial function?

A: To find the other root of a polynomial function, you can take the negative of the imaginary part of the given complex root.

Q: What is the equation for the polynomial function?

A: The equation for the polynomial function is given by (x - 2 - i)(x - 2 + i)(x - 5) = 0.

Q: Can a polynomial function have only one complex root?

A: No, a polynomial function cannot have only one complex root. If a polynomial function has a complex root, then its conjugate is also a root of the function.

Q: How do I determine if a polynomial function has complex roots?

A: To determine if a polynomial function has complex roots, you can use the quadratic formula to find the roots of the function. If the discriminant is negative, then the function has complex roots.

Q: Can a polynomial function have complex roots with a non-zero real part?

A: Yes, a polynomial function can have complex roots with a non-zero real part.

Q: How do I find the complex roots of a polynomial function?

A: To find the complex roots of a polynomial function, you can use the quadratic formula to find the roots of the function. If the discriminant is negative, then the function has complex roots.

Q: Can a polynomial function have complex roots with a zero imaginary part?

A: No, a polynomial function cannot have complex roots with a zero imaginary part. If a polynomial function has a complex root, then its imaginary part is non-zero.

Q: How do I determine if a polynomial function has complex roots with a non-zero imaginary part?

A: To determine if a polynomial function has complex roots with a non-zero imaginary part, you can use the quadratic formula to find the roots of the function. If the discriminant is negative and the imaginary part of the root is non-zero, then the function has complex roots with a non-zero imaginary part.

Conclusion

In this article, we have answered some frequently asked questions about complex roots of polynomial functions. We have discussed the conjugate root theorem, how to find the other root of a polynomial function, and how to determine if a polynomial function has complex roots.

Frequently Asked Questions

What is the conjugate root theorem?
How do I find the other root of a polynomial function?
What is the equation for the polynomial function?
Can a polynomial function have only one complex root?
How do I determine if a polynomial function has complex roots?
Can a polynomial function have complex roots with a non-zero real part?
How do I find the complex roots of a polynomial function?
Can a polynomial function have complex roots with a zero imaginary part?
How do I determine if a polynomial function has complex roots with a non-zero imaginary part?

References

[1] "Complex Numbers" by Math Open Reference
[2] "Polynomial Functions" by Khan Academy
[3] "Algebra" by MIT OpenCourseWare