# Chapter 7 - Exponents and Exponential Functions - 7-1 Zero and Negative Exponents - Practice and Problem-Solving Exercises - Page 418: 46

At d=-2, which means 2 decades before the finches population started increasing, the population was 20. At d=0, which means that the initial population of finches was 45. At d=1, which means after 1 decade, the population of finches was 67 finches.

#### Work Step by Step

P(d)=45$\times$$1.5^{d} P(-2)=45\times$$1.5^{-2}$ =$\frac{45}{1.5^{2}}$ = $\frac{45}{2.25}$ = 20 P(0)=45$\times$$1.5^{0} = 45 \times 1 = 45 P(1)=45\times$$1.5^{1}$ = 45 $\times$ 1.5 = 67.5 so 67 finches as you can't have half of a finch.

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