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7th Grade · Math

Expanding and Factoring Expressions

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Concept Review

The Distributive Property: Breaking Down the Big Picture

Imagine you're organizing a school fundraiser. You need to buy 4 packages, and each package contains 12 cookies plus 8 juice boxes. How do you quickly calculate the total items? You could count everything individually, or you could use math's most powerful shortcut: the distributive property.

The distributive property lets us "distribute" or spread out multiplication over addition. Instead of solving complicated expressions all at once, we can break them into smaller, manageable pieces. Think of it like unpacking a suitcase—you take out one item at a time rather than dumping everything out together.

The Mathematical Magic

The distributive property follows this pattern: a(b + c) = ab + ac

The number outside the parentheses gets "distributed" to every term inside. Let's see this in action with our fundraiser example:

Step-by-Step: 4(12 + 8)

Original expression: 4(12 + 8)
Distribute the 4: 4 × 12 + 4 × 8
Calculate each part: 48 + 32
Final answer: 80 total items

Notice how we multiplied the 4 by both the 12 and the 8 separately, then added the results.

Why Does This Work?

Think about it logically: if you have 4 groups of (12 + 8), that's the same as having 4 groups of 12 plus 4 groups of 8. We're just rearranging how we count the same total amount—like sorting your Halloween candy by type before counting versus counting the whole pile at once.

💡 Key Insight

The distributive property doesn't change the answer—it changes the process. Whether you calculate 4(12 + 8) = 4(20) = 80 or 4(12 + 8) = 48 + 32 = 80, you get the same result. But the distributed form often makes complex expressions much easier to work with.

More Than Just Numbers

This property works with any combination of numbers and eventually with variables too. Try 3(5 + 7 + 2): distribute the 3 to get 3 × 5 + 3 × 7 + 3 × 2 = 15 + 21 + 6 = 42. The same principle applies whether you're working with two terms or ten terms inside those parentheses.

🔑 Key Takeaway

Just like organizing that school fundraiser by breaking down the big picture into manageable pieces, the distributive property helps us tackle complex mathematical expressions by distributing the work. Master this property, and you'll have a powerful tool for simplifying expressions and solving problems efficiently.

Sample questions

1. Expand: 3(x + 5)
3x + 15
3x + 5
x + 15
3x + 8
Answer: 3x + 15 — 3 × x = 3x, 3 × 5 = 15, so 3x + 15.
2. Apply the distributive property: 4(2x + 3)
6x + 7
8x + 12
8x + 3
4x + 12
Answer: 8x + 12 — 4 × 2x = 8x, 4 × 3 = 12, so 8x + 12.
3. Expand: 5(3x + 2)
8x + 7
15x + 2
15x + 10
5x + 10
Answer: 15x + 10 — 5 × 3x = 15x, 5 × 2 = 10, so 15x + 10.

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