The Rules of Multiplying Polynomials

Oct 13, 2025 by wbrum.org 42 views

Understanding the Problem

In this problem, we are given the expression $${-2 y^9(-7 y)}$$ and we need to simplify it as much as possible. To do this, we will use the rules of multiplying polynomials.

The Rules of Multiplying Polynomials

When multiplying polynomials, we need to follow the distributive property, which states that:

$a(b + c) = ab + ac$

This means that we need to multiply each term in the first polynomial by each term in the second polynomial.

Multiplying the Polynomials

Let's start by multiplying the two polynomials:

{-2 y^9(-7 y)}

We can start by multiplying the $-2$ by the $-7y$ :

$-2 \cdot -7y = 14y$

Next, we need to multiply the $y^9$ by the $-7y$ :

$y^9 \cdot -7y = -7y^{10}$

Now, we can combine the two terms:

$14y - 7y^{10}$

Simplifying the Expression

The expression $14y - 7y^{10}$ is already simplified, but we can simplify it further by combining like terms.

Combining Like Terms

Like terms are terms that have the same variable and exponent. In this case, we have two like terms: $14y$ and $-7y^{10}$ .

We can combine these terms by adding or subtracting their coefficients:

$14y - 7y^{10} = 14y - 7y^{10}$

Since there are no like terms to combine, the expression is already simplified.

Conclusion

In this problem, we multiplied two polynomials using the distributive property and simplified the resulting expression. We also combined like terms to simplify the expression further.

Key Takeaways

When multiplying polynomials, we need to follow the distributive property.
We can simplify the resulting expression by combining like terms.
The expression $14y - 7y^{10}$ is already simplified.

Practice Problems

Multiply the polynomials: $3x^2(2x + 5)$
Simplify the expression: $-4y^3(2y + 3)$
Multiply the polynomials: $-2x^3(3x - 2)$

Answer Key

$6x^3 + 15x^2$
$-8y^4 - 12y^3$
$-6x^4 + 4x^3$

Additional Resources

Khan Academy: Multiplying Polynomials
Mathway: Multiplying Polynomials
Wolfram Alpha: Multiplying Polynomials

References

"Algebra" by Michael Artin
"Calculus" by Michael Spivak
"Mathematics for Computer Science" by Eric Lehman and Tom Leighton
Multiplying Polynomials: A Q&A Guide =====================================

Frequently Asked Questions

Q: What is the distributive property?

A: The distributive property is a rule of multiplying polynomials that states that:

$a(b + c) = ab + ac$

This means that we need to multiply each term in the first polynomial by each term in the second polynomial.

Q: How do I multiply polynomials?

A: To multiply polynomials, we need to follow the distributive property. We multiply each term in the first polynomial by each term in the second polynomial and then combine like terms.

Q: What are like terms?

A: Like terms are terms that have the same variable and exponent. For example, $2x^2$ and $3x^2$ are like terms because they both have the variable $x$ and the exponent $2$ .

Q: How do I combine like terms?

A: To combine like terms, we add or subtract their coefficients. For example, if we have the terms $2x^2$ and $3x^2$ , we can combine them by adding their coefficients:

$2x^2 + 3x^2 = 5x^2$

Q: What is the difference between multiplying polynomials and multiplying numbers?

A: When multiplying numbers, we simply multiply the numbers together. When multiplying polynomials, we need to follow the distributive property and multiply each term in the first polynomial by each term in the second polynomial.

Q: Can I use a calculator to multiply polynomials?

A: Yes, you can use a calculator to multiply polynomials. However, it's often easier to multiply polynomials by hand, especially for simple expressions.

Q: How do I simplify a polynomial expression?

A: To simplify a polynomial expression, we need to combine like terms and eliminate any unnecessary terms.

Q: What is the order of operations when multiplying polynomials?

A: The order of operations when multiplying polynomials is:

Multiply each term in the first polynomial by each term in the second polynomial.
Combine like terms.
Simplify the resulting expression.

Q: Can I multiply polynomials with different variables?

A: Yes, you can multiply polynomials with different variables. For example, if we have the polynomials $x^2 + 3x$ and $y^2 + 2y$ , we can multiply them together:

$(x^2 + 3x)(y^2 + 2y) = x^2y^2 + 2xy^3 + 3xy^2 + 6y^3$

Q: How do I multiply polynomials with negative coefficients?

A: When multiplying polynomials with negative coefficients, we need to follow the rules of multiplying negative numbers. For example, if we have the polynomials $-2x^2$ and $3x^2$ , we can multiply them together:

$(-2x^2)(3x^2) = -6x^4$

Q: Can I multiply polynomials with fractional coefficients?

A: Yes, you can multiply polynomials with fractional coefficients. For example, if we have the polynomials $\frac{1}{2}x^2$ and $3x^2$ , we can multiply them together:

$(\frac{1}{2}x^2)(3x^2) = \frac{3}{2}x^4$

Q: How do I multiply polynomials with exponents?

A: When multiplying polynomials with exponents, we need to follow the rules of multiplying exponents. For example, if we have the polynomials $x^2$ and $x^3$ , we can multiply them together:

$x^2 \cdot x^3 = x^{2+3} = x^5$

Q: Can I multiply polynomials with radicals?

A: Yes, you can multiply polynomials with radicals. For example, if we have the polynomials $\sqrt{x}$ and $\sqrt{x}$ , we can multiply them together:

$\sqrt{x} \cdot \sqrt{x} = \sqrt{x^2} = x$

Q: How do I multiply polynomials with complex numbers?

A: When multiplying polynomials with complex numbers, we need to follow the rules of multiplying complex numbers. For example, if we have the polynomials $2 + 3i$ and $4 - 5i$ , we can multiply them together:

$(2 + 3i)(4 - 5i) = 8 - 10i + 12i - 15i^2$

Since $i^2 = -1$ , we can simplify the expression:

$8 - 10i + 12i - 15(-1) = 8 - 10i + 12i + 15 = 23 + 2i$

Q: Can I use a calculator to multiply polynomials with complex numbers?

A: Yes, you can use a calculator to multiply polynomials with complex numbers. However, it's often easier to multiply complex numbers by hand, especially for simple expressions.

Q: How do I multiply polynomials with matrices?

A: When multiplying polynomials with matrices, we need to follow the rules of matrix multiplication. For example, if we have the matrices:

$A = \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix}$

$B = \begin{bmatrix} 5 & 6 \\ 7 & 8 \end{bmatrix}$

We can multiply them together:

$AB = \begin{bmatrix} 1 \cdot 5 + 2 \cdot 7 & 1 \cdot 6 + 2 \cdot 8 \\ 3 \cdot 5 + 4 \cdot 7 & 3 \cdot 6 + 4 \cdot 8 \end{bmatrix}$

$AB = \begin{bmatrix} 19 & 22 \\ 43 & 50 \end{bmatrix}$

Q: Can I use a calculator to multiply polynomials with matrices?

A: Yes, you can use a calculator to multiply polynomials with matrices. However, it's often easier to multiply matrices by hand, especially for simple expressions.

Q: How do I multiply polynomials with vectors?

A: When multiplying polynomials with vectors, we need to follow the rules of vector multiplication. For example, if we have the vectors:

$\mathbf{a} = \begin{bmatrix} 1 \\ 2 \end{bmatrix}$

$\mathbf{b} = \begin{bmatrix} 3 \\ 4 \end{bmatrix}$

We can multiply them together:

$\mathbf{a} \cdot \mathbf{b} = 1 \cdot 3 + 2 \cdot 4 = 11$

Q: Can I use a calculator to multiply polynomials with vectors?

A: Yes, you can use a calculator to multiply polynomials with vectors. However, it's often easier to multiply vectors by hand, especially for simple expressions.

Q: How do I multiply polynomials with functions?

A: When multiplying polynomials with functions, we need to follow the rules of function multiplication. For example, if we have the functions:

$f(x) = x^2 + 3x$

$g(x) = 2x + 1$

We can multiply them together:

$f(x) \cdot g(x) = (x^2 + 3x)(2x + 1)$

$= 2x^3 + x^2 + 6x^2 + 3x$

$= 2x^3 + 7x^2 + 3x$

Q: Can I use a calculator to multiply polynomials with functions?

A: Yes, you can use a calculator to multiply polynomials with functions. However, it's often easier to multiply functions by hand, especially for simple expressions.

Q: How do I multiply polynomials with trigonometric functions?

A: When multiplying polynomials with trigonometric functions, we need to follow the rules of trigonometric function multiplication. For example, if we have the functions:

$f(x) = \sin(x) + \cos(x)$

$g(x) = \sin(x) - \cos(x)$

We can multiply them together:

$f(x) \cdot g(x) = (\sin(x) + \cos(x))(\sin(x) - \cos(x))$

$= \sin^2(x) - \cos^2(x)$

Q: Can I use a calculator to multiply polynomials with trigonometric functions?

A: Yes, you can use a calculator to multiply polynomials with trigonometric functions. However, it's often easier to multiply trigonometric functions by hand, especially for simple expressions.

Q: How do I multiply polynomials with exponential functions?

A: When multiplying polynomials with exponential functions, we need to follow the rules of exponential function multiplication. For example, if we have the functions:

$f(x) = e^x + e^{-x}$

$g(x) = e^x - e^{-x}$

We can multiply them together:

$f(x) \cdot g(x) = (e^x + e^{-x})(e^x - e^{-x})$

$= e^{2x} - e^{-2x}$

Q: Can I use a calculator to multiply polynomials with exponential functions?

A: Yes, you can use a calculator to multiply polynomials with exponential functions. However, it's often easier to multiply exponential functions by hand, especially for simple expressions.

Q: How do I multiply polynomials with logarithmic functions?

A: When multiplying polynomials with logarithmic functions, we