Mastering the Basics: How to Factor the Expression x² - 9

• A. (x + 9)(x - 9)
• B. (x - 3)(x - 3)
• C. (x + 3)(x - 3)
• D. (x + 2)(x - 2)

Answer: (C)

Unpacking the Puzzle: How to Factor x² - 9

Hey there, future math whizzes! If you’re preparing for the Ontario Mathematics Proficiency Test, you've probably stumbled across expressions like x² - 9 and wondered how to factor them efficiently. Well, today's your lucky day, because we’re going to break it down step-by-step, making it as easy as pie!

What Does Factoring Mean?

Before diving into the specifics of x² - 9, let’s get on the same page about what factoring is. In simpler terms, when we factor an expression, we’re rewriting it as a product of simpler expressions (or factors) that can be multiplied together to get the original expression back. Think of it like taking apart a Lego building to see how each piece fits together.

The Difference of Squares Explained

Now, the expression x² - 9 is a classic example of what we call a difference of squares. Are you scratching your head? No worries! This just means we can express it in the form a² - b², where:

• a is x

• b is 3 (because 9 is 3 squared.)

By recognizing this, we can use the formula for the difference of squares, which states:

a² - b² = (a + b)(a - b).

So, let’s apply this to our expression!

Factorization Step-by-Step

1. Identify a and b:

• Here, a = x

• b = 3

2. Plug those values into the formula:

x² - 3² = (x + 3)(x - 3).

And there you have it! The factored form of x² - 9 is (x + 3)(x - 3). Pretty snazzy, right?

What's This All About?

You might be wondering, why go through all this trouble? Well, knowing how to factor helps you find the roots of the equation x² - 9 = 0. When you set each factor to zero:

• x + 3 = 0 ➔ x = -3

• x - 3 = 0 ➔ x = 3

So, the solutions are x = 3 and x = -3. These roots tell us where the graph of the equation intersects the x-axis, which is super handy in algebra and beyond!

What About the Wrong Answers?

If you’ve taken a stab at the multiple-choice options, you might have noticed other tempting answers:

• A. (x + 9)(x - 9)

• B. (x - 3)(x - 3)

• C. (x + 3)(x - 3) (Our winner!)

• D. (x + 2)(x - 2)

Each of these options represents a different algebraic expression, and a quick multiplication of each will show you they don’t equal x² - 9. Stick to the formula, and you can avoid those tricky distractions!

Why It Matters in Your Study Journey

Understanding how to factor expressions isn’t just a checkbox on a test; it’s a fundamental math skill that’ll serve you well. Whether you’re solving equations, graphing functions, or even studying calculus, factoring is like having a trusty tool in your math toolbox. You know what I mean? The more familiar you are with it, the more confident you’ll feel tackling tougher problems.

Wrap Up

So, next time you encounter an expression like x² - 9, remember this—it’s a difference of squares! Now you’ve got a nifty formula in your back pocket, and with a bit of practice, you’ll be able to factor even the trickiest expressions with ease.

Keep practicing, stay engaged, and let the numbers guide your way as you prepare for the Ontario Mathematics Proficiency Test. Good luck, and happy factoring!