Set 9: Quadratic Equations (Intermediate)

Explanation

Answer: A

A rocket is launched. Its height is $h(t) = -16t^2 + 128t$ . How long is the rocket in the air?

8 seconds

✓ Correct

4 seconds

16 seconds

128 seconds

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Find when it hits the ground ( $h=0$ ). 1. $-16 t^2 + 128 t = 0$ . 2. Factor: $-16 t(t - 8) = 0$ . 3. Roots: $t=0$ (launch) and $t=8$ (landing). 4. Total time in air is 8 seconds. Choice B is incorrect because it is the time to max height. Choice C is incorrect. Choice D is incorrect.

Key Steps:

•

The correct answer is 8 seconds

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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