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Published byJoy Holt Modified over 8 years ago
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2-3 Multiplying and Dividing Rational Numbers
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Ex. 1 Multiplying Same Signs ▫ Always positive answer 2(2) = 4 or -2(-2) = 4 Different Signs ▫ Always a negative answer 4(-6) = -24 Simplify ▫ -10(-5) = ▫ 50
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Ex 1. Cont. Your practice ▫ -2/3(3/4) = ▫ -6/12 = ▫ -1/2
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Ex. 2 Evaluating Evaluate -2xy for x = -20 and y = -3 ▫ Plug and chug -2(-20)(-3) = -120 -2(-3)(cd) for c = -8 and d = -7 Put parenthesis around negatives ▫ -2(-3)((-8)(-7)) = 6(56) = 336
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Ex. 2 Cont. Your practice Evaluate ▫ 8p ∙ (-2n) for p = -1 and n = 3 8(-1) ∙ (-2(3)) = -8 ∙ (-6) = 48
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Ex. 3 Story Problems Use the expression given and then evaluate ▫ t = -5.5(a/1000) for a = altitude ▫ a = 8000 t = -5.5(8000/1000) t = -5.5(8) t = -44 Your practice ▫ Quick check number 3
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Ex. 4 Simplifying Exponents Use PEMDAS Simplify ▫ -3 4 = -1 ∙ (3*3*3*3) = -81 ▫ (-3) 4 (-3)(-3)(-3)(-3) = 81
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Ex. 4 cont. Your Practice ▫ -5 2 (-3) 3 = -1(5*5) ∙ (-27) = -25 ∙ (-27) = 625
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Ex. 5 Dividing Same signs ▫ Always a positive answer (-20)/(-10) = 2 or (20)/(10) = 2 Different signs ▫ Always a negative answer (-20)/(10) = -2 or (20)/(-10) = -2 Simplify ▫ (3-14)/2 = (-11)/2 = -11/2 or -5 1/2 Your practice ▫ -56/(4+3) = -56/7 = -8
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Ex. 6 Evaluating Evaluate –x/(-4) + 2y ÷ z for x = -20, y = 6, and z = -1 ▫ -(-20)/(-4) + 2(6) ÷ (-1) = 20/(-4) +12 ÷ (-1) = -5 + (-12) = -17 Your practice Evaluate (2z + x)/(2y) for x = 8, y = -5, and z = -3 ▫ (2(-3) + 8)/(2(-5)) (-6 + 8)/(-10) 2/-10 -1/5
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Ex. 7 Division Using Reciprocal x/y is x ÷ y ▫ (-3/4)/(-5/2) is (-3/4) ÷ (-5/2) K eep C hange F lip ▫ (-3/4) ∙ (-2/5) – Multiply straight across ▫ (6/20) = ▫ 3/10 Your practice ▫ -3m/t for m = 5/6 and t = 1/6 -3(5/6) ÷ 1/6 = -15/6 ÷ 1/6 = -15/6 ∙ 6/1 = -90/6 = -15
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