## onegirl 2 years ago Match the graphs of the functions on the left with the graphs of their derivatives on the right.

1. onegirl

2. onegirl

3. onegirl

4. ZeHanz

Do you know what the derivative of a 2nd degree function is?

5. onegirl

no

6. ZeHanz

You know the following I guess: If f is decreasing, then f' is negative (and vice versa). If f is increasing, then f' is positive ( and vv).

7. onegirl

yes

8. ZeHanz

No look at the first graph on the left. To the left of the y-axis, it is decreasing, to the right it is increasing.

9. onegirl

yes it does

10. ZeHanz

This means, for f' you are looking for a function that is negative on the left side of the y-axis and positive on the right.

11. onegirl

ok

12. onegirl

so it will be #2 in the second attachment?

13. ZeHanz

I can see it on one of your drawings on the right! Do you?

14. onegirl

Yes it will be number 2 ?

15. onegirl

so to will have letter A

16. ZeHanz

No, I've got C

17. onegirl

but you can't match a with c , it says to match the left with the right so it has to be a letter with a number

18. ZeHanz

I mean this (see image) The parabola on the left (2nd degree function) has the straight line on the right as it's derivative.

19. onegirl

so number one will be 1 with letter c?

20. onegirl

I meant number 2 sorry

21. onegirl

so 2C ?

22. ZeHanz

Yes

23. onegirl

okay

24. ZeHanz

Now try #2. See what it does: increasing, decreasing, increasing. So you're looking for a graph that is +, then -, then +.

25. onegirl

i thought we already did number 2

26. onegirl

?

27. zepdrix

He was telling you number #1 is C. There musta been some confusion there c:

28. onegirl

ohhh okay lol sorry

29. onegirl

so number 2 will be f?

30. ZeHanz

@zepdrix: thx

31. ZeHanz

Yes!

32. onegirl

okay :)

33. ZeHanz

I think you got it!

34. onegirl

number 3 looks funny

35. zepdrix

I think #2 is `e` actually :o hmm

36. ZeHanz

It is down, up, down, up, so look for -,+,-,+

37. onegirl

okay so number 3 will be A ?

38. ZeHanz

@zepdrix : you're right, I'm having trouble looking at three different pictures, @onegirl: sorry ;)

39. onegirl

okay thanks for the correction zep

40. onegirl

so 3A ?

41. ZeHanz

Yes, 3A

42. onegirl

okay

43. onegirl

so number 4 will be D?

44. ZeHanz

Right again! Always decreasing, so looking for a derivative that is always negative...

45. onegirl

okay

46. onegirl

so i'm guessing number 5 will be 5B?

47. onegirl

?

48. ZeHanz

You guessed wrong... Look at graph #5 and compare with #3

49. ZeHanz

It behaves in the same way: dec, inc, dec, inc, so -,+,-,+

50. onegirl

ok so it will be 5f

51. ZeHanz

Oops, look something went wrong with my last response. Because 5 and 3 behave in the same way, you have to choose the same derivative: 5A

52. onegirl

ohh ok

53. onegirl

so letter A goes to two graphs? okay

54. ZeHanz

That's the mean part of the question ;)

55. onegirl

okay so how about the last one number 6?

56. ZeHanz

It goes down, then up, then down, so for f' we have: neg, pos, neg

57. onegirl

so it will be 6B

58. ZeHanz

No, that goes a lot more from - to + etc.

59. ZeHanz

(it is really simple)

60. onegirl

ohh so it will f since it does go negative pos then neg

61. ZeHanz

Yes, it's 6F. I must admit this kind of question can be confusing, because you constantly have to switch from increasing , decreasing to +, -.

62. onegirl

okay well thanks for your help