Equations with the Distributive Property
When an equation has parentheses, like , the first job is to get rid of them. The distributive property does that: multiply the number outside the parentheses by each term inside.
After you distribute, the parentheses are gone and what's left is a two-step equation you already know how to solve. Distribute first, then solve — that's the whole lesson.
Distribute first
means three copies of the whole quantity . The distributive property multiplies the by each term inside: . So the equation becomes .
The most common mistake is multiplying only the first term — writing instead of . The outside number multiplies every term inside the parentheses, not just the one it touches.
Distributing a negative
If the outside number is negative, its sign travels with the multiplication. becomes : the times gives , and the times gives . Both terms change, and a negative times a negative comes out positive.
A shortcut: divide both sides first
When the outside number divides evenly into the other side, you can divide both sides by it instead of distributing. In , dividing both sides by gives , so .
Use whichever route you like — distributing always works, and the shortcut is nice when the division is clean.
Worked examples
Example 1: distribute a positive number
Solve .
Answer:
Example 2: a two-term inside expression
Solve .
Answer:
Example 3: distribute a negative number
Solve .
Answer:
Try one yourself
Common questions
Do I always have to distribute first?
No. If the outside number divides evenly into the other side, dividing both sides by it is faster: becomes in one move. But distributing works on every problem, so it's the safe default.
What happens when I distribute a negative number?
Every term inside the parentheses picks up the sign. is , not — the times is a positive . Sign errors here are the number one source of wrong answers in this topic.
What if there's more outside the parentheses, like ?
Distribute first, then combine like terms: becomes , so and . Clearing the parentheses is always the opening move.
How do I check my answer?
Substitute it into the original equation, parentheses and all. For : is true, so the answer checks.
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