Thursday

September 3, 2015
Posted by **Melinda** on Saturday, December 3, 2011 at 11:50am.

1. Which function has a negative average rate of change on the interval 1<x<4

a) f(x) = x^2 - x - 1

b) g(x) = 1.6x - 2

c) h(x) = -x^2 + 9

d j(x) = -3

I picked d, because I subsitute all the numbers for all letters and the only negative one was D because there is no x value to add in.

----------------------------------

2. For which value of x is the instantaneous rate of change of h(x) = 0.5x^2 + x - 2 closest to 0?

a) x= -1

b) x= -1

c) x= 0

d x= 1

I chose B

--------------------------------------

3. A student is walking in a straight line in front of a motion sensor. What does he need to do to produce a horizontal segment on the distance versus time graph?

a) move quickly toward the sensor

b) move slowly toward the sensor

c) stand in place

d) move quickly away from the sensor

The answer is c.

--------------------------------

4. A student is walking in a straight line in front of a sensor. The sensor begins collecting data when the student is 6m away. The student walks toward the sensor for 4 s at a rate of 0.5 m/s. Which of the points on the graph of the distance versus time graph for this walk?

a) (6, 0)

b) (8,2)

c) (10,6)

d) (12,6)

I chose D.

Help appreciated~

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 12:17pm2. For which value of x is the instantaneous rate of change of h(x) = 0.5x^2 + x - 2 closest to 0?

a) x= -1

b) x= 0

c) x= 1

d x= 3

sorry mistake on #2

its B?

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 12:48pmProblem 1.

The answer is NOT D.

The average rate of change is:

for x=1, f(1)=-3

for x=4, f(4)=-3

Average rate of change is 0, not a negative number. One of the answers does give a negative average rate of change.

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 12:56pmProblem 2.

The answer is not B, (x=0).

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:01pmFor Number 1, the answer is A

wow, totally miscalculated.

What about other questions am I right?

For number 3

4. A student is walking in a straight line in front of a sensor. The sensor begins collecting data when the student is 6m away. The student walks toward the sensor for 4 s at a rate of 1 m/s.

Then she walks away from the sensor for 8 s at a rate of 0.5 m/s.Which of the points on the graph of the distance versus time graph for this walk?

a) (6, 0)

b) (8,2)

c) (10,6)

d) (12,6)

*Sorry, forgot one part of the question T.T I chose D, (12,6)

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 1:11pmProblem 1

A is not the answer.

f(4)- f(1)

=11 - (-1)

= +12

--------------

Problem 3.

C looks correct

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:14pmWhy is problem 1 not A? I plugged in 4 and 1 into each of the equations given and A gave me negative avg rate T.T

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 1:23pmFor a distance vs time graph. X axis is time and Y axis is distance.

at t=6s, dist=5m

at t=8s, dist=6m

at t=10s, dist=7m

at t=12s, dist=8m

I don't see any of those as choices.

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 1:25pmProblem 1.

Look at my calculation, the average rate is +12,not a negative number.

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:25pmThis is the correct question, sorry I forgot to type in the one part of the question.

4. A student is walking in a straight line in front of a sensor. The sensor begins collecting data when the student is 6m away. The student walks toward the sensor for 4 s at a rate of 1 m/s.

Then she walks away from the sensor for 8 s at a rate of 0.5 m/s.Which of the points on the graph of the distance versus time graph for this walk?

a) (6, 0)

b) (8,2)

c) (10,6)

d) (12,6)

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:31pmThen the answer must be c)

h(x) = -x^2 + 9/4-1

= -(4)^2 + 9/4-1

= -7/4-1

=-x(1)^2 + 9

= 8

= -7 - 8/3

=-5

there c is negative

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 1:41pmC is the answer I got.

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:43pmFor problem 2, it is A? x= -1

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 1:46pmFor problem 2, I got A, x=-1.

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:48pmWhat about question 4?

4. A student is walking in a straight line in front of a sensor. The sensor begins collecting data when the student is 6m away. The student walks toward the sensor for 4 s at a rate of 1 m/s.

Then she walks away from the sensor for 8 s at a rate of 0.5 m/s.Which of the points on the graph of the distance versus time graph for this walk?

a) (6, 0)

b) (8,2)

c) (10,6)

d) (12,6)

I got D

- precalculus -
**Quidditch**, Saturday, December 3, 2011 at 1:52pmWith the values given, I did not find any of the answers on the graph.

For a distance vs time graph. X axis is time and Y axis is distance.

at t=6s, dist=5m

at t=8s, dist=6m

at t=10s, dist=7m

at t=12s, dist=8m

I don't see any of those as choices.

- precalculus -
**Melinda**, Saturday, December 3, 2011 at 1:55pmI believe its between (10,6) and (12,6) because we know that the starting point is at 6..

I don't know after that