6

Set 10: Exponential Functions

Explanation

Answer: A

A population model is P(t)=500001+Ae0.8tP(t) = \frac{50000}{1 + Ae^{-0.8t}}. If P(0)=5000P(0) = 5000, what is AA?

A.

A=9A = 9

✓ Correct
B.

A=10A = 10

C.

A=5A = 5

D.

A=45A = 45

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Use the initial condition to find AA. 1. At t=0t=0: 5000=500001+Ae0=500001+A5000= \frac{50000}{1 + Ae^0} = \frac{50000}{1 + A}. 2. Multiply: 5000(1+A)=500005000(1 + A) = 50000. 3. Divide: 1+A=101+ A = 10. 4. Solve: A=9A = 9. 5. Verify: P(0)=500001+9=5000P(0) = \frac{50000}{1 + 9} = 5000 ✓ Strategic Tip: Initial condition gives P0=K1+AP_0 = \frac{K}{1+A}, so A=KP01A = \frac{K}{P_0} - 1. Choice B is incorrect because this would give P(0)=50000114545P(0) = \frac{50000}{11} \approx 4545. Choice C is incorrect because this would give P(0)=5000068333P(0) = \frac{50000}{6} \approx 8333. Choice D is incorrect because this would give P(0)=50000461087P(0) = \frac{50000}{46} \approx 1087.

Key Steps:

The correct answer is A=9A = 9

Why others are wrong:
B: Choice B is incorrect and may result from a calculation error.
C: Choice C is incorrect and may result from a calculation error.
D: Choice D is incorrect and may result from a calculation error.

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