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Advanced Math / Nonlinear functions Difficulty: Medium

An object is kicked from a platform. The equation $h = - 4.9 t^{2} + 7 t + 9$ represents this situation, where $h$ is the height of the object above the ground, in meters, $t$ seconds after it is kicked. Which number represents the height, in meters, from which the object was kicked?

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Explanation

Choice D is correct. It’s given that the equation $h = - 4.9 t^{2} + 7 t + 9$ represents this situation, where $h$ is the height, in meters, of the object $t$ seconds after it is kicked. It follows that the height, in meters, from which the object was kicked is the value of $h$ when $t equals 0$ . Substituting $0$ for $t$ in the equation $h = - 4.9 t^{2} + 7 t + 9$ yields $h = - 4.9 {(0)}^{2} + 7 (0) + 9$ , or $h equals 9$ . Therefore, the object was kicked from a height of $9$ meters.

Choice A is incorrect and may result from conceptual or calculation errors.

Choice B is incorrect and may result from conceptual or calculation errors.

Choice C is incorrect and may result from conceptual or calculation errors.