Final answer:
The time for the space curve is 3.960 seconds, after considering significant figures and rounding to three decimal places, with the negative time solution discarded as non-physical.
Step-by-step explanation:
The question asks us to find the time for a space curve where a given equation yields two solutions for time: t = 3.96 s and a negative solution. Since negative time implies an event occurring before the start of motion which isn't physically meaningful in this context, we discard it. Thus, the correct time is t = 3.96 s. It is important to note that when rounding, we must consider significant figures. Each value given has three significant figures; therefore, our answer should also maintain that level of precision. The final answer, reflecting the appropriate significant figures and rounding, is t = 3.960 s when rounded to three decimal places.