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I am refreshing algebra to get ready for calculus and i have a problem and my book doesn't explain it well.

take this equation simplification

-15(x/3) = -5 * 3 * (x * 1/3)

Now, when i distribute the 3 to eliminate the parens, i get

-5 * 3x * 1 = -5 * 3x

the book says thats wrong,

how do you get -5x for the answer? im missing something

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2 Answers 2

The 3s cancel on the rhs. You multiplied by 9. $$\frac{(-5)(3)(x)}{3}=-5x$$

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You are trying to distribute as if it were an addition not a product. So $5*3*(x*1/3) = 5*3*x*1/3 = 5x$. what you're doing is multiplying 3 by x and 1/3.

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