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Big Ideas Math: Modeling Real Life, Grade 7

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Big Ideas Math: Modeling Real Life, Grade 7 View details

Practice Test

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Exercise 8 Page 42

Instead of subtracting a negative number, you can add.

11

Let's perform the subtraction. Subtracting a negative number is the same as adding its positive counterpart.

2-(-9)

a-(- b)=a+b

2+9

Add terms

11

Below we will demonstrate by finding 2 and moving 9 units to the right on the number line.

The resulting position, after moving to the right on the number line, is the difference. 2-(-9)=11

Extra

Properties of Real Numbers

When we are performing mathematical operations using real numbers, we always need to make sure that we are following the Properties of Real Numbers.

Distributive Property
Commutative Property of Addition
Commutative Property of Multiplication
Associative Property of Addition
Associative Property of Multiplication

These properties tell us the legal moves we can make when adding or multiplying numbers.

But why aren't there properties for subtraction or division?

Some mathematicians refuse to acknowledge that subtraction and division are even operations! Subtraction is the same thing as adding a negative and division is the same thing as multiplying by a fraction. a-b=a+(- b) and a/b=a* 1/b Therefore, we can use the Properties of Real Numbers for subtraction and division, but we need to change our way of thinking.

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