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Distributive Property

The distributive property multiplies the number outside parentheses by each term inside: a(b+c)=ab+aca(b + c) = ab + ac. In 4(x+5)4(x + 5), the 44 multiplies the xx and it multiplies the 55, giving 4x+204x + 20. Both terms get the multiplication — that is the whole property.

You need this move because x+5x + 5 cannot be combined into one term, so the multiplication cannot wait for the parentheses to finish. Distributing is how algebra clears parentheses, and it shows up in nearly every equation you will solve after this unit.

Multiply each term inside

Draw two arrows in your head — one from the outside number to each inside term. For 3(x+7)3(x + 7): 3x=3x3 \cdot x = 3x and 37=213 \cdot 7 = 21, so 3(x+7)=3x+213(x + 7) = 3x + 21.

The most common error is multiplying only the first term: writing 3(x+7)=3x+73(x + 7) = 3x + 7. Check yourself by counting terms — two terms inside the parentheses means two multiplications, every time.

Subtraction inside the parentheses

Treat the subtraction as a negative term riding along. 4(x9)4(x - 9) means 4x4 \cdot x and 4(9)4 \cdot (-9), which gives 4x364x - 36. The minus sign inside survives into the answer.

A negative number outside

When the outside number is negative, it multiplies each term — sign included. 5(2m+4)-5(2m + 4) gives 52m=10m-5 \cdot 2m = -10m and 54=20-5 \cdot 4 = -20, so the answer is 10m20-10m - 20.

And when negative meets negative, the product is positive: 3(2x5)=6x+15-3(2x - 5) = -6x + 15. Every sign inside the parentheses gets flipped by a negative distributor. If exactly one sign flipped and the other did not, go back and find the error.

Worked examples

Example 1: a positive number outside

Distribute 3(x+7)3(x + 7).

Multiply 33 by the first term3x=3x3 \cdot x = 3x
Multiply 33 by the second term37=213 \cdot 7 = 21
Write both products3x+213x + 21

Answer: 3x+213x + 21

Example 2: subtraction inside

Distribute 4(x9)4(x - 9).

Multiply 44 by the first term4x=4x4 \cdot x = 4x
Multiply 44 by the negative term4(9)=364 \cdot (-9) = -36
Write both products4x364x - 36

Answer: 4x364x - 36

Example 3: a negative number outside

Distribute 5(2m+4)-5(2m + 4).

Multiply 5-5 by the first term52m=10m-5 \cdot 2m = -10m
Multiply 5-5 by the second term54=20-5 \cdot 4 = -20
Write both products10m20-10m - 20

Answer: 10m20-10m - 20

Try one yourself

Common questions

Why can't I just add what's inside the parentheses first?

If the inside is all numbers, you can — 4(2+5)=47=284(2 + 5) = 4 \cdot 7 = 28 works fine. But x+5x + 5 cannot be added into a single term, so distributing is the only way to clear the parentheses.

What happens with a negative outside and a minus inside?

The two negatives multiply to a positive. 3(2x5)=6x+15-3(2x - 5) = -6x + 15. Every term inside gets its sign flipped by the negative distributor — if only one term flipped, there is a sign error.

What if there are three terms inside the parentheses?

Distribute to all three. 2(x+3y4)=2x+6y82(x + 3y - 4) = 2x + 6y - 8. The number outside multiplies every term inside, no matter how many there are.

Does distributing work with a variable outside?

Yes, the same way. x(x+3)=xx+x3=x2+3xx(x + 3) = x \cdot x + x \cdot 3 = x^{2} + 3x. The outside factor multiplies each term inside, whether it is a number, a variable, or both.

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