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Section 8-1: Zero and Negative Exponents Objectives: (1) To understand that numbers in the real number system are represented in a variety of equivalent forms (2) To add, subtract, multiply and divide exponential expressions Properties • Zero Exponent Property – For every nonzero number a, a0 = 1 • Examples – 50 = 1 (-2)0 = 1 (-1.02)0 = 1 (1/2)0 = 1 • Negative Exponent Property – For every nonzero number a and integer n, 1 -n a =a n • Examples – 6-4 = 1 64 (-8)-1 = 1 8 Converting Negative Exponents to Positive Exponents • Step 1: Make every number with a negative exponent a fraction (easiest way to convert any number into a fraction is putting it over 1) • Step 2: Move the number to the other side of the fraction bar and change the sign • Step 3: If there are no numbers left on one side of the fraction bar, put a 1 to represent that there was a number there originally. Examples of Converting Negative Exponents • 4-3 • 1_ 43 • 1 _____ 4•4•4 • 1__ 64 This is what we call simplifying a power Simplifying an Exponential Expression Simplify the expression 4yx-3 1 4 y 3 x 4y X3 • Use the definition of negative exponents • Simplify • We’re done! • Tada! Simplifying an Exponential Expression Simplify the expression: 1 w-4 w4 • Move the w to the other side of the fraction bar • You’re done! • Tada! Evaluating Exponential Expressions Evaulate: 3m2t-2 for t = -3, m = 2 3m2 t2 3(2)2 (-3)2 3(4) 9 12 9 4 3 • 1st: Convert to positive exponents • 2nd: Plug in values (put them in parenthesis) • 3rd : Simplify • You’re done Real-World Problem Solving • Population Growth: A biologist is studying green peach aphids (a bug). In the lab, the population doubles every week. The expression 1000 • 2w models an initial population of 1000 insects after w weeks of growth. a. Evaluate the expression for w = 0. Then describe what the value of the expression represents in the situation. b. Evaluate the expression for w = -3. Then describe what the value of the expression represents in the situation. Part A 1000 • 2w 1000 • 20 1000 • 1 1000 • Plug in 0 for w • Now evaluate • What does 1000 represent? • The initial number of aphids Part B 1000 • 2w 1000 • 2-3 1000 • 13 2 1000 • 125 1 8 • Plug in -3 for w • Now evaluate • What does 125 represent? • The number of aphids 3 weeks ago