# Section 2.5 – Multiplying Real Numbers Int. Math I.

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Section 2.5 – Multiplying Real Numbers Int. Math I

Rules for multiplying real numbers: Rule #1: A product is negative if it has an odd number of negative factors. Example: -3 x -2 x -4 = -24, 3 (odd) negatives equals a negative!!!

Rule #2: A product is positive if it has an even number of negative factors. Example: -3 x -5 x 4 = 60, 2 negatives (even) equals a positive!!!

Try these problems: Find the product. 1. -4(5)2. -2(5)(-3) 3. -2(4)(5)4. (-2)(-2)(-2)(-2)

Properties of Multiplication!!! Commutative Property of Multiplication: ab = baExample: 2 x 3 = 3 x 2 Associative Property of Multiplication: (ab)c = a(bc)Example: (-6 x 2)3 = -6(2 x 3)

Identity Property: 1 x a = aExample: 1 x 3 = 3 Property of Zero: 0 x a = 0Example: 0 x 5 = 0

More examples to discuss: Simplify the expressions. 1. 6(-x)2. –x(-x)(-x) 3. -3(-y) 3 4. Evaluate the expression for the given value of the variable. (a) -8(d) when d = 6(b) 9(-2)(-r) 3 when r = 2

Try these problems: Simplify the expressions. 1. -10(-x)2. –y(-y)(-y)(-y) 3. -4(-x) 5 4. Evaluate the expression for the given value of the variable. (a) 3(-4)(n) when n = -2(b) -3(-a) when a = -7

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