## math456 4 years ago I need help, anyone?

1. math456

Q. 2,3, 5?

2. Kreshnik

do you have a graph yet? ... I can get you one !

3. math456

|dw:1333410736966:dw| yea its like this!

4. Kreshnik

...

5. math456

ohh i c :)

6. math456

so for Q.2 we have to graph the inverse, right?

7. Kreshnik

is this what is required at option a)?? ...I don't get it well enough (I'm not American/British :S )

8. Kreshnik

two lines... f(x)=4x-8 and y=x

9. math456

umm we have to find inverse first which is x+8/4=y and graphing it gives me |dw:1333411085687:dw|

10. Kreshnik

$\Large f^{-1}(x) =\frac{1}{f(x)}$ ... so that should be . .$\LARGE f^{-1}(x)=\frac{1}{4x-8}$ is it??

11. math456

and ur graph is answer to part 5

12. math456

umm our teacher tell us that u switch letters first & then solve for y to get the inverse..

13. math456

do u know how to do Q.3?

14. Kreshnik

I know it like I wrote it !! O_O ... show me your way then!

15. Kreshnik

are you there?

16. math456

yea

17. math456

i already told u inverse seems like x+8/4=y

18. math456

or f^-1(x)

19. math456

what does it mean to test the symmetry accross the line y=x?

20. Kreshnik

I don't know it either... but tell me, how do you get x+8/4=y ... show me steps I want to see them if it's possible ! O_O

21. math456

lol okay..

22. math456

y=f(x)=4x-8 x=4y-8 (switched) x+8/4=y (solve for y)

23. Kreshnik

still dizzy... I don't know.. OK now tell me if we have $\LARGE f(x)=\frac{1-x}{1+x}$ how does f^{-1} go?

24. slaaibak

the inverse of f(x) is not 1/f(x)

25. Kreshnik

ok I guess I'm wrong, but I want to learn it.. :(

26. slaaibak

To find the inverse, switch x and y, and write in terms of y.

27. Kreshnik

well then @math456 is right !!...

28. math456

f(x)=1-x/1+x x=1-y/1+y x(1+y)=1-y x+xy=1-y y=1-x+xy

29. math456

y=1-x-xy*

30. math456

????

31. slaaibak

y = (1 - x)/(1 + x) Switching the x and y: x = (1-y)/(1+y) x + xy = 1 - y y(1+x) = 1-x y = (1-x)/(x+1)

32. slaaibak

with which number do you need help with?

33. math456

Q.2 a,b

34. math456

i mean like for a we hv to reflect the graph of f across the diagonal line y=x, how?

35. slaaibak

draw the y=x line and flip the line over it

36. slaaibak

I mean, flip it over the line

37. math456

|dw:1333412317919:dw| like this?

38. math456

fliping it will be|dw:1333412361021:dw|

39. slaaibak

That's y=x yes. Best way to see it is to draw the line, then folding the paper over y=x and to see how the graph reflects

40. slaaibak

Noo... you flip the function f(x) over the line y=x.

41. math456

so for Q2a we hv to flip over the f(x) ?

42. math456

or the inverse?

43. slaaibak

flip f(x) over y=x

44. math456

ohh okay!

45. math456

|dw:1333412477378:dw| so its gona be like this?

46. math456

how about 2b? and question 5 ask the same thing as 2a, right?

47. slaaibak

noooo |dw:1333412696801:dw|

48. slaaibak

question 2 b: get a few points (x,y) then change them to (y,x) and draw them

49. math456

and 5 is |dw:1333412939248:dw| ?

50. slaaibak

Not exactly sure what they mean..

51. math456

so for 2b i got a graph like this |dw:1333413313588:dw|

52. slaaibak

... I honestly don't know how you got that. Look at my graph. Thats how f, y=x and f^-1 looks like

53. math456

that was for f(x) and if I reflect it, i'll get |dw:1333413484096:dw|

54. math456

with Question 5?