5

Set 8: Exponential Functions

Explanation

Answer: A

An exponential function passes through the points (0,10)(0, 10) and (1,20)(1, 20). What is the equation of the function?

A.

y=10(2)xy = 10(2)^x

✓ Correct
B.

y=20(0.5)xy = 20(0.5)^x

C.

y=10+10xy = 10 + 10x

D.

y=2(10)xy = 2(10)^x

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Use the points to find aa and bb. 1. Find a: The y-intercept is (0,10)(0, 10), so a=10a = 10. 2. Find b: The function passes through (1,20)(1, 20). Substitute into y=10bxy = 10 b^x: 20=10b120= 10 b^1. 3. Solve: 20=10b    b=220= 10 b \implies b = 2. 4. Equation: y=10(2)xy = 10(2)^x. Strategic Tip: The point (1,y)(1, y) tells you the value of a×ba \times b. Divide by aa to get bb. Choice B is incorrect because it represents decay. Choice C is incorrect because it is a linear function. Choice D is incorrect because it swaps the initial value and the base.

Key Steps:

The correct answer is y=10(2)xy = 10(2)^x

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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