Question

I'm about to cry right now, please help me.

The graph below shows the distance (y) in kilometers of two cars from their destination at different times (x) in minutes. The table shows the values plotted on the graph.

Time
(in minutes)
x 0 10 20 30 40 50
Car 1
(in km)
y 50 40 30 20 10 0
Car 2
(in km)
y 50 40.85365 33.3804 27.2742 22.285 18.2085

Part C: What is the domain of the functions for car 1 and car 2?

Part D: What is the average rate of change from x = 20 to x = 40 for the function representing the motion for car 2? What does the value of this average rate of change re

Answer 1

Ah don't cry

The domain is the x values. Can you list the x values?

Answer 2

Yeah, 0, 10, 20, 30, 40, 50. So, The domain for the functions of Car 1 and Car 2 is 0, 10, 20, 30, 40, 50.

Answer 3

?

Answer 4

So x ranges from 0<=x<=50

It ranges from 0 to 50

Answer 5

Ok. Got it. :-) Could you please help me w/ D.?

Answer 6

Now the rate of change is a division. x/y , which is time over distance

Answer 7

Right, I got for my answer as -0.55477. Which I was told was wrong.

Answer 8

y2 - y1 over x2 over x1

Answer 9

That's the formula for finding the slope of two points, which is the correct formula to use.

Answer 10

right

Answer 11

but...my answer is incorrect.

Answer 12

I'm confused with the y values given. At f(0) is y = 50 ? ?

Answer 13

Time
(in minutes)
x 0 10 20 30 40 50
Car 1
(in km)
y 50 40 30 20 10 0
Car 2
(in km)
y 50 40.85365 33.3804 27.2742 22.285 18.2085

Answer 14

yes

Answer 15

Then at f(20) y = 33.3804?
And at f(40) y = 22.285

It confuses me that the numbers are going down.

Answer 16

@KirbyLegs help please

Answer 17

for D, I also got -0.55477

maybe they want you to round this value ?
otherwise, make a note of this question and ask your teacher about it.

***It confuses me that the numbers are going down.***
the numbers are the distance from the destination. As the car gets closer, the distance goes down. The line has negative slope

Answer 18

Ok. So, the average rate of change is -0.55477, and it represents what exactly? :)

Answer 19

the slope (the -0.55..) is how much the distance is changing per minute
in other words, every minute the distance goes down by (because it's negative) by 0.55477 km. In 20 minutes, the distance goes down by
-0.55477 km/min * 20 mins = -11.0954 km
and if we check, we see that is true. at time 20 the distance was 33.3804
and 20 minutes later the distance is 22.285

Answer 20

Ok, so it is correct, -0.55477?

Answer 21

Yes. Make a note and ask your teacher about this one.

Answer 22

I meant would you mind helping me w/ another one?

Answer 23

ok

Answer 24

Sam is observing the velocity of a car at different times. After three hours, the velocity of the car is 51 km/h. After five hours, the velocity of the car is 59 km/h.

Part A: Write an equation in two variables in the standard form that can be used to describe the velocity of the car at different times.

Part B: How can you graph the equation obtained in Part A for the first six hours?

Answer 25

I think they want you to say, for example, x= time in hours
y = velocity
if we use those variables, we have 2 (x,y) points: (3,51) and (5,59)

for B) find the equation of the line through those 2 pts

Answer 26

Part A: y = 4x + 39 = v = 4t + 39

Answer 27

is that what they were asking for?

Answer 28

Oh, you are correct. That is what they want

but they want the equation in standard form

Answer 29

So, it'd be: x + y = 4 and...how would-wait. Give me a second.

Answer 30

The Standard Form is -4x + y = 39

Answer 31

yes, but generally I would make the x coefficient positive
in other words, multiply both sides (and all terms) by -1 to get
4x - y = -39

Answer 32

Why would I do this?

Answer 33

@phi how would I answer part B.?

Answer 34

according to wikipedia
In the general (or standard[1]) form the linear equation is written as:
Ax + By = C,
where A and B are not both equal to zero.
***The equation is usually written so that A ≥ 0, by convention.***

Answer 35

Part B sounds dumb.

How can you graph the equation obtained in Part A for the first six hours?

I would plot the two points (3,51) and (5,59)
and draw a line through those points, from x=0 to x= 6

Answer 36

Thank you, it does sound strange, doesn't it? XD