Help with pre-calculus questions

[watchthesky30]

I need help with some of these questions. Thanks!:
1) find a function whose graph is the given curve
a. the bottom half of the circle x²+y²=9
Would the answer just be f(x) = ?(9-x²), -3?x?3? i know that's the answer for the top half. So would the bottom half be the same?

2) sketch the graph of the function by first making a table of values
a. f(X)=x/|x|
the tables of values went from 1-5 and it was just a horizontal line. I'm not sure if this is right.

3) A man is running around a circular track 200m in circumference. An observer uses a stopwatch to record the runer's time at the end of each lap, obtaining the data in the following table.
a) What was the man's average speed (rate) between 68s and 152s?
This is what i did, although i'm not sure if my answer is correct.
The circumference formula is c=2?r
so average rate of change = c(152)-c(68)/152-68
= (2?(152))-(2?(68))/84 and so on.

 

[daon]

1. It says bottom half. You've given the top half. the bottom is just the reflection over the x axis.

2. that function is -1 when x<0 and 1 when x>=0. so from 1-5 it should be 1.

 

[stapel]

1) Don't forget that there's a "plus / minus" when you take the square root of each side! :wink:

2) Are you familiar with what absolute values are? (You didn't show your work or values; what you've posted leaves this unclear.)

3) We can't see the table you're looking at, so we cannot comment on your use of the values contained therein. Sorry!