## .Sam. 3 years ago A problem Solve for x, 7.3^(x-1)+5-3^(x+1)=0

1. .Sam.

$\huge 7.3^{x-1}+5-3^{x+1}=0$

2. perl

is that 7*3^(x-1) or (7.3)^(x-1)

3. .Sam.

decimal

4. perl

hmmm, doesnt look easy

5. lgbasallote

do tell me..does this involve canceling 3^x-1 the solution i thought had that..

6. Ishaan94

$3^x = \frac{15}{2}$ $x = \log_3 \frac{15}2$

7. .Sam.

@Ishaan94 that's true if the decimal was "dot" *

8. Ishaan94

Oh, my bad... so it's $(7.3)^{x-1} + 5-3^{x+1}=0$Hmm Now I feel stupid :/

9. perl

ok I have an idea

10. perl

|dw:1333364793236:dw|

11. perl

|dw:1333364860619:dw|

12. Ishaan94

campbell decimal point, 7.3 = 73/10

13. Ishaan94

:/

14. perl

its an annoying problem. whats the bloody solution?

15. anonymoustwo44

ln(a+b) is not the same as lna +lnb

16. Ishaan94

You can't take log like that

17. Ishaan94

I think 7.3 has something to do with 5, we should try to use 5

18. perl

did sam leave,

19. experimentX
20. perl

why did he say this is easy problem

21. karatechopper

hhe says its easy and im still stuck on first step, can i switch signs?

22. Ishaan94

Who is hhe?

23. karatechopper

i meant he, meaning sam

24. perl

i think this could somehow become a quadratic, with the right substitution

25. perl

|dw:1333366072740:dw|

26. experimentX

i don't think general method we use would work

27. experimentX

how do you solve this 2^x - x = 2

28. anonymoustwo44

I think we could only use newtons method......

29. anonymoustwo44

30. perl

i want an EXACT solution

31. anonymoustwo44

then use the newton's method to get a better aproximation

32. anonymoustwo44

we continue this until we're satisfied

33. anonymoustwo44

but we can't still get the exact though :(

34. perl

summon sam

35. experimentX

currently the best way to solve is graphical method ... lol

36. anonymoustwo44

yeah

37. anonymoustwo44

the number 5 is irritating

38. perl

i sent sam a message, he better respond .

39. perl

40. Ishaan94

@satellite73

41. satellite73

i assume that is $$7.3^{x-1}$$ and not $$7\cdot 3^{x-1}$$ so i have no ideas yet

42. satellite73

must be something special about 7.3 that i do not see

43. perl

can you guys tell me later, i gotta sleep

44. perl

ok try this , let u = 3^(x+1)

45. perl

i assume there is an exact solution, otherwise youve wasted my time

46. .Sam.

I can see that you guys think so hard, lol

47. perl

48. .Sam.

Sad thing for you @perl There's no exact solution but approximation $7.3^{x-1}=3^{x+1}-5$

49. Mimi_x3

i knew that newtoms method of approximation yesterday..

50. anonymoustwo44

I TOLD YOU SO

51. Mimi_x3

from yesterday*

52. perl

it would be more interesting if there was exact solution , :(

53. perl

i was confused since you said it was easy problem , rats

54. anonymoustwo44

newton's method :D

55. anonymoustwo44

newton's method :D

56. perl

ok then how is it easy to approximate?

57. .Sam.

Its easy you don't even need to think, lol

58. perl

what?

59. perl

it didnt look easy on wolfram

60. perl

sam , so are you going to post the solution or not. cuz im getting really tired

61. perl

you can use a calculator for this. is that your 'easy' solution ?

62. .Sam.

you have to graph it for 7.3^(x-1) and 3^(x+1)-5 pick some points

63. perl

what program do you use to graph that?

64. .Sam.

its a tedious job though, but if you have a graphing calc, it will be fine

65. perl

then why do you say its easy?

66. perl
67. perl

what do you mean , pick some points? estimate

68. .Sam.

yes , estimate

69. Mimi_x3

Newtons Method i think..

70. perl

i dont think so, its just approximation problem

71. Mimi_x3

then what else?

72. perl

anyways, the question seemed pretty ambiguous. i didnt know what they meant by 'easy'

73. Mimi_x3

lol, thats all? guessing?

74. .Sam.

you can use this program to graph https://www.desmos.com/calculator/c

75. perl

then you do screen capture?

76. Mimi_x3

sigh..you can state your question as finding the approximation than 'solve for x'

77. .Sam.

@Mimi_x3 yes its a bit of disappointing, but I'll come up with a new question later :)

78. .Sam.

@perl no i dont screen cap on that software

79. Mimi_x3

lol, i wanted to see a solution..but there is no solution *sigh*

80. .Sam.

the solution is approximation ,lol

81. Mimi_x3

like the working out..

82. .Sam.

Nevermind I'll come up a new one :)

83. Mimi_x3

84. perl

so you copy as a file

85. perl

I think there is a confusion, he copied the problem originally with multiplication 7*3^(x-1)

86. apoorvk

c'mon i got the approximate thing using 'jugaad' :/

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