Writing Quadratic Expressions in Standard Form

Oct 13, 2025 by wbrum.org 51 views

Understanding Quadratic Expressions

A quadratic expression is a polynomial expression of degree two, which means the highest power of the variable is two. It can be written in the form of ${ax^2 + bx + c}$ , where ${a}$ , ${b}$ , and ${c}$ are constants, and ${x}$ is the variable. In this lesson, we will learn how to write quadratic expressions in standard form by multiplying and simplifying the given expressions.

Writing Quadratic Expressions in Standard Form

a. ${$ (x-2)(x+5)$}$

To write the quadratic expression ${(x-2)(x+5)}$ in standard form, we need to multiply the two binomials using the FOIL method.

FOIL Method

The FOIL method is a technique used to multiply two binomials. It stands for First, Outer, Inner, Last, which refers to the order in which we multiply the terms.

First: Multiply the first terms of each binomial: ${x \cdot x = x^2}$
Outer: Multiply the outer terms of each binomial: ${x \cdot 5 = 5x}$
Inner: Multiply the inner terms of each binomial: ${-2 \cdot x = -2x}$
Last: Multiply the last terms of each binomial: ${-2 \cdot 5 = -10}$

Now, let's combine the terms:

${$ x^2 + 5x - 2x - 10$}$

Combine like terms:

${$ x^2 + 3x - 10$}$

Therefore, the quadratic expression ${(x-2)(x+5)}$ in standard form is ${x^2 + 3x - 10}$ .

b. ${$ (4x-1)(3x-2)$}$

To write the quadratic expression ${(4x-1)(3x-2)}$ in standard form, we need to multiply the two binomials using the FOIL method.

Using the FOIL method, we get:

First: Multiply the first terms of each binomial: ${4x \cdot 3x = 12x^2}$
Outer: Multiply the outer terms of each binomial: ${4x \cdot -2 = -8x}$
Inner: Multiply the inner terms of each binomial: ${-1 \cdot 3x = -3x}$
Last: Multiply the last terms of each binomial: ${-1 \cdot -2 = 2}$

Now, let's combine the terms:

${ $12x^2 - 8x - 3x + 2\$}$

Combine like terms:

${ $12x^2 - 11x + 2\$}$

Therefore, the quadratic expression ${(4x-1)(3x-2)}$ in standard form is ${12x^2 - 11x + 2}$ .

Discussion

Consider the expression ${ $8(1-x)-x(1+x)\$}$ . Is the expression a quadratic expression?

To determine if the expression is a quadratic expression, we need to simplify it.

Using the distributive property, we get:

${ $8(1-x) = 8 - 8x\$}$

${$ -x(1+x) = -x - x^2$}$

Now, let's combine the terms:

${ $8 - 8x - x - x^2\$}$

Combine like terms:

${$ -x^2 - 9x + 8$}$

Therefore, the expression ${ $8(1-x)-x(1+x)\$}$ is a quadratic expression in standard form.

Conclusion

Frequently Asked Questions

Q: What is a quadratic expression?

A: A quadratic expression is a polynomial expression of degree two, which means the highest power of the variable is two. It can be written in the form of ${ax^2 + bx + c}$ , where ${a}$ , ${b}$ , and ${c}$ are constants, and ${x}$ is the variable.

Q: How do I write a quadratic expression in standard form?

A: To write a quadratic expression in standard form, you need to multiply the two binomials using the FOIL method and combine like terms.

Q: What is the FOIL method?

A: The FOIL method is a technique used to multiply two binomials. It stands for First, Outer, Inner, Last, which refers to the order in which we multiply the terms.

Q: How do I use the FOIL method?

A: To use the FOIL method, you need to multiply the first terms of each binomial, then the outer terms, then the inner terms, and finally the last terms. Then, combine the terms to simplify the expression.

Q: What is the difference between a quadratic expression and a polynomial expression?

A: A polynomial expression is a general term that refers to any expression that can be written in the form of ${a_nx^n + a_{n-1}x^{n-1} + \ldots + a_1x + a_0}$ , where ${a_n \neq 0}$ . A quadratic expression is a specific type of polynomial expression where the highest power of the variable is two.

Q: Can a quadratic expression have a negative coefficient?

A: Yes, a quadratic expression can have a negative coefficient. For example, the quadratic expression ${-x^2 + 3x - 2}$ has a negative coefficient.

Q: Can a quadratic expression have a fraction as a coefficient?

A: Yes, a quadratic expression can have a fraction as a coefficient. For example, the quadratic expression ${\frac{1}{2}x^2 + \frac{3}{4}x - \frac{1}{3}}$ has fractions as coefficients.

Q: How do I determine if an expression is a quadratic expression?

A: To determine if an expression is a quadratic expression, you need to simplify it and check if it can be written in the form of ${ax^2 + bx + c}$ , where ${a}$ , ${b}$ , and ${c}$ are constants, and ${x}$ is the variable.

Q: Can a quadratic expression have a variable as a coefficient?

A: No, a quadratic expression cannot have a variable as a coefficient. For example, the expression ${x^2 + 3x^2 - 2}$ is not a quadratic expression because it has a variable as a coefficient.

Q: Can a quadratic expression have a negative variable as a coefficient?

A: No, a quadratic expression cannot have a negative variable as a coefficient. For example, the expression ${-x^2 + 3x - 2}$ is a quadratic expression, but the expression ${-x^2 - 3x - 2}$ is not a quadratic expression because it has a negative variable as a coefficient.

Conclusion

In this Q&A article, we answered some of the most frequently asked questions about writing quadratic expressions in standard form. We covered topics such as the FOIL method, polynomial expressions, and determining if an expression is a quadratic expression. We hope this article has been helpful in clarifying any doubts you may have had about quadratic expressions.