Читать книгу Algebra I All-in-One For Dummies - Mary Jane Sterling, Mary Sterling Jane - Страница 53

When you multiply two or more signed numbers, you just multiply them without worrying about the sign of the answer until the end. Then, to assign the sign, just count the number of negative signs in the problem. If the number of negative signs is an even number, the answer is positive. If the number of negative signs is odd, the answer is negative.

The product of two signed numbers:

The product of more than two signed numbers:

  has a positive answer because there are an even number of negative factors.

  has a negative answer because there are an odd number of negative factors.

Q.

A. Multiply the two factors without their signs, and you get 6. There are two negative signs in the problem, so the result is positive. The answer is +6.

Q.

A. There are three negative signs in the problem, so the result is negative. The product of the numbers (without their signs) is 24. The answer is –24.

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