C) explain why David's average speed is less than his top speed.​

Explanation:

His top speed is a blip that occurs for less than the full time he was out. Below is a graph showing what he did from 1 o'clock to 9. He was walking from 1 to the point where starts walking faster and then back down again to 2. The line at 2 is longer than the triangular shape that shows where he speeded up. Then he went back down to 2 and continued at that speed until 9.

Obviously he spent more time at 2 than he did at 4 and therefore his average speed will less than the 4 speed.

Remember that average speed = total distance / total time.

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.