Set 12: Quadratic Equations

Explanation

Answer: A

A tunnel is shaped like a parabola $y = -0.2x^2 + 5$ . How wide is the tunnel at the base ( $y=0$ )?

10 m

✓ Correct

5 m

25 m

20 m

Detailed Explanation

Choice A is correct. Choice A is the correct answer. Find the x-intercepts. 1. $-0.2 x^2 + 5 = 0$ . 2. $0.2x^2 = 5$ . 3. $x^2 = 25$ . 4. $x = \pm 5$ . 5. Width = Distance between -5 and 5 = $5- (-5) = 10$ meters. Choice B is incorrect because it is the half-width. Choice C is incorrect. Choice D is incorrect.

Key Steps:

•

The correct answer is 10 m

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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