## bigoldnastyfish one year ago The price of products may increase due to inflation and decrease due to depreciation. Derek is studying the change in the price of two products, A and B, over time. The price f(x), in dollars, of product A after x years is represented by the function below. f(x) = 10250(0.63)x Part A: Is the price of product A increasing or decreasing and by what percentage per year? Justify your answer. (5 points) Part B: The table below shows the price f(t), in dollars, of product B after t years. t (number of years) 1 2 3 4 f(t) (price in dollars) 4300 1849 795.07 341.88

1. bigoldnastyfish

Which product recorded a greater percentage change in price over the previous year? Justify your answer. (5 points)

2. dmezzullo

Is this an exam?

3. bigoldnastyfish

no its the study guide

4. bigoldnastyfish

could you help me?

5. kewlgeek555

Do you still need help?

6. bigoldnastyfish

yes

7. kewlgeek555

Okay, I am really sorry, but I have to eat. Though, I can explain this question perfectly to you. So, I'll be back in like 20 to 30 minutes - i hope thats okay.

8. bigoldnastyfish

that is totally fine im just studying had a question on this problem

9. kewlgeek555

I am back. Sorry for being three minutes late.

10. bigoldnastyfish

its ok haha

11. kewlgeek555

12. kewlgeek555

When it doesn't say that "Kewlgeek555 is typing a reply..." it is because I am thinking or doing work. ;]

13. kewlgeek555

Part I: You know that this function is DECREASING because 0.63, the number inside of the parenthesis, is LESS THAN THE NUMBER 1. I [think I] know the way to determine by what percentage it is decreasing. [I think] My teacher taught me that I have to subtract the number, in this case 0.63, from 1. So, 1 - 0.63 = 0.37. So it is decreasing by 0.37. Part II: Wait, what are the directions asking you to do???

14. bigoldnastyfish

Which product recorded a greater percentage change in price over the previous year? Justify your answer. (5 points)

15. kewlgeek555

Okay, this is for the table in Part B, correct?

16. bigoldnastyfish

correct

17. kewlgeek555

And is this the table of Part B: |dw:1387393002341:dw| Is this correct? Also, I have to go do soemthing for my job, be back in like less than ten minutes, more than five minutes.

18. bigoldnastyfish

t (number of years) 1 2 3 4 f(t) (price in dollars) 4300 1849 795.07 341.88

19. kewlgeek555

I am back. I am still confused. Do you have a picture or something? But, now I think I understand A LITTLE. Is this correct?: |dw:1387394201440:dw|

20. bigoldnastyfish

yup

21. kewlgeek555

Okay. Then, I think it is year 1 - 2.

22. bigoldnastyfish

can you prove it?

23. kewlgeek555

Well, I subtracted years 1 - 2, 2 - 3, 3 - 4, and 1 - 2 was the greatest difference. I just didn't want to because what I said right there is a horrid "prove it" sentence. So, I can't really prove it.

24. kewlgeek555

NO, no. Actually, they are all changing by the same percentage: 43% less. And you can prove it by dividing year 2 to year 1 and dividing year 3 to year 2. Sorry for the inaccurate answer.

25. bigoldnastyfish

OOOOOOO I see

26. bigoldnastyfish

do you think you could help me with 1 more question?

27. bigoldnastyfish

Belinda wants to invest \$1000. The table below shows the value of her investment under two different options for two different years. Number of years 1 2 3 Option 1 (amount in dollars) 1300 1690 2197 Option 2 (amount in dollars) 1300 1600 1900

28. bigoldnastyfish

Part B: Write one function for each option to describe the value of the investment f(n), in dollars, after n years. (4 points) Part C: Belinda wants to invest in an option that would help to increase her investment value by the greatest amount in 20 years. Will there be any significant difference in the value of Belinda's investment after 20 years if she uses option 2 over option 1? Explain your answer and show the investment value after 20 years for each option. (4 points)

29. kewlgeek555

Where is Part A? Please tag me as several people are requesting help right now. D:

30. bigoldnastyfish

All i really need to know is the percentage of what option 1 is growing at

31. bigoldnastyfish

Part A: What type of function, linear or exponential, can be used to describe the value of the investment after a fixed number of years using option 1 and option 2? Explain your answer. (2 points)

32. bigoldnastyfish

33. kewlgeek555

Oh, oh, okay. Well, um. Hm...do you have the function equation? Or the value at year 0?

34. bigoldnastyfish

there is no year 0

35. kewlgeek555

Okay, so did you make a function?

36. bigoldnastyfish

I just need to know at what percentage option 1 changes at

37. bigoldnastyfish

Thats all I need to do

38. bigoldnastyfish

I can do the rest after that

39. kewlgeek555

This also seems to be a constant rate of growth. Year 2, 1690, is year 1 times 1.3. And year 3, 2197, is year 2 times 1.3. So, the rate of growth must be 130% of year 0, or in other words f(0) * 1.3.

40. kewlgeek555

I hope I'm not confusing.

41. bigoldnastyfish

what is the rate of chagne of option 1 as a percentage

42. kewlgeek555

Okay, I don't know now. My mind is like something else today. Let me call @jigglypuff314 @texaschic101 @agent0smith @terenzreignz for you.

43. jigglypuff314

I'm not too good at this either ;) http://www.ehow.com/how_8117999_exponential-equation-two-points.html I got that the equation for option 1 is d = 1000(1.3^n) if that helps...

44. bigoldnastyfish

I figured it out thank you guys :D

45. sosakiing

wht did you get cause i got the same problemand im so lost

46. Secret-Ninja

Lies. This IS an exam. *smh*

47. bloofoffiction

The only way you would know that is by looking up the question during the test as well @Secret-Ninja

48. ro561man

not really she could have seen this question and remembered on her test...right @secret-ninja