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Distributive Property (cont)

Expressions like 3(5x+2)83(5x + 2) - 8 need two moves, in a fixed order: distribute first, then combine like terms. Distributing clears the parentheses, and once everything is out in the open, the like terms collapse together the usual way.

The order is not negotiable. The 8-8 in 3(5x+2)83(5x + 2) - 8 cannot touch the 22 while the 22 is still locked inside the parentheses with a 33 waiting to multiply it. Distribute, and only then combine.

The two-move routine

Move 1 — distribute: multiply the outside number by each term inside the parentheses. 3(5x+2)83(5x + 2) - 8 becomes 15x+6815x + 6 - 8.

Move 2 — combine like terms: 68=26 - 8 = -2, so the answer is 15x215x - 2. The variable term had nothing to pair with, so it rides through unchanged.

A minus sign in front of the parentheses

In 153(4x2)15 - 3(4x - 2), the number being distributed is 3-3 — the minus sign belongs to it. Distributing gives 1512x+615 - 12x + 6. Notice the last term became +6+6, because 3(2)=6-3 \cdot (-2) = 6.

Then combine: 15+6=2115 + 6 = 21, so the answer is 2112x21 - 12x. The classic mistake is subtracting 15315 - 3 first to get 12(4x2)12(4x - 2) — but multiplication binds before subtraction, so the 33 must distribute before anything is subtracted.

A lone variable joins in

In x+3(2x4)x + 3(2x - 4), the xx out front just waits its turn. Distribute: x+6x12x + 6x - 12. Combine, remembering the lone xx has a coefficient of 11: 1x+6x=7x1x + 6x = 7x. The answer is 7x127x - 12.

Worked examples

Example 1: distribute, then combine constants

Simplify 4(2x+5)94(2x + 5) - 9.

Distribute the 448x+2098x + 20 - 9
Combine the constants209=1120 - 9 = 11
Write the result8x+118x + 11

Answer: 8x+118x + 11

Example 2: a minus sign distributes

Simplify 153(4x2)15 - 3(4x - 2).

Distribute 3-3 to both terms1512x+615 - 12x + 6
Combine the constants15+6=2115 + 6 = 21
Write the result2112x21 - 12x

Answer: 2112x21 - 12x

Example 3: a lone variable joins in

Simplify x+3(2x4)x + 3(2x - 4).

Distribute the 33x+6x12x + 6x - 12
Combine the xx terms1x+6x=7x1x + 6x = 7x
Write the result7x127x - 12

Answer: 7x127x - 12

Try one yourself

Common questions

In 153(4x2)15 - 3(4x - 2), why can't I do 15315 - 3 first?

Order of operations — multiplication comes before subtraction. The 33 is attached to the parentheses by multiplication, so it must distribute first. The 1515 waits until the parentheses are gone.

Do I distribute the minus sign too?

Yes. In 153(4x2)15 - 3(4x - 2) you distribute 3-3, not 33. Both inside terms feel it: 34x=12x-3 \cdot 4x = -12x and 3(2)=+6-3 \cdot (-2) = +6. Distributing 33 and then subtracting the whole result also works, but treating the number and its sign as one package causes fewer errors.

How do I know when I'm done simplifying?

No parentheses remain, and no two remaining terms are like terms. 8x+118x + 11 is done — a variable term and a constant cannot combine. If you can still spot a matching pair, keep going.

What about a bare minus in front, like (2x7)-(2x - 7)?

A bare minus means a coefficient of 1-1. Distribute it: (2x7)=2x+7-(2x - 7) = -2x + 7. Every sign inside gets flipped.

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