Staredit Network > Forums > Null > Topic: Help With Homework, plzthx :D
Help With Homework, plzthx :D
Aug 30 2009, 2:28 am
By: ProtoTank
Pages: < 1 2 3 4 >
 

Aug 30 2009, 7:45 am DT_Battlekruser Post #21



It's called the Quadratic Formula in English (x = (-b +/- sqrt(b2 - 4ac)) / 2a).

Yes, you are correct. Your answer also evaluates to 2.26, which is a nice check. Algebra is a bitch.




None.

Aug 30 2009, 9:10 am MasterJohnny Post #22



yeah.. I am not seeing how to work it out with the quadratic formula. Can you elaborate more?



I am a Mathematician Computer Scientist Logic user

Aug 30 2009, 9:33 am Jack Post #23

>be faceless void >mfw I have no face

Quadratic equation works once you have your equation in the form ax^2+bx+c. So for this problem, a = 2^x, and b = -5, and c = 1. Then you put those into the quadratic equation and the anrwer is what x equals.



Red classic.

"In short, their absurdities are so extreme that it is painful even to quote them."

Aug 30 2009, 10:38 am Clokr_ Post #24



Oh god, a solve my homework topic...

Anyway...

Quote
2^x + 2^(-x) = 5
When solving an exponential equation the simplest way is to get all the powers to look the same. In this case you got 2^x and 2^(-x) which can be easily converted to 1/2^x:

2^x + 1/2^x = 5

Now you do a = 2^x to get a standard equation:

a + 1/a = 5

You solve it for a:

(a²+1)/a = 5 -> a²+1 = 5a -> a² - 5a + 1 = 0
so a = (5ħsqrt(25-4))/2 = (5ħsqrt(21))/2
Since a = 2^x then 2^x = (5ħsqrt(21))/2 and thus x = log2 ((5ħsqrt(21))/2)
Solved ^^



?????

Aug 30 2009, 10:39 am BeDazed Post #25



Actually in this case, a was 1 and x itself was 2^x.



None.

Aug 30 2009, 2:56 pm Dapperdan Post #26



Didn't there used to be a rule against posting topics for people to do your homework?



None.

Aug 30 2009, 3:05 pm Symmetry Post #27

Dungeon Master

No, homework solving threads have been quite common over the past few iterations of SEN.



:voy: :jaff: :voy: :jaff:

Aug 30 2009, 3:23 pm ProtoTank Post #28



Quote from Clokr_
Oh god, a solve my homework topic...

Anyway...

Quote
2^x + 2^(-x) = 5
When solving an exponential equation the simplest way is to get all the powers to look the same. In this case you got 2^x and 2^(-x) which can be easily converted to 1/2^x:

2^x + 1/2^x = 5

Now you do a = 2^x to get a standard equation:

a + 1/a = 5

You solve it for a:

(a²+1)/a = 5 -> a²+1 = 5a -> a² - 5a + 1 = 0
so a = (5ħsqrt(25-4))/2 = (5ħsqrt(21))/2
Since a = 2^x then 2^x = (5ħsqrt(21))/2 and thus x = log2 ((5ħsqrt(21))/2)
Solved ^^

I remember browsing through some topics in serious discussion, I saw a couple of calculations at your hands. I was hoping you would come along! :D



I'm only here because they patched SC1 and made it free.

Aug 30 2009, 3:24 pm Clokr_ Post #29



Quote from Dapperdan
Didn't there used to be a rule against posting topics for people to do your homework?

I wouldn't mind helping to solve homework as long as they ask how and not what is the answer.
Still SEN might not be the right place to ask this kind of questions.

Quote from ProtoTank
I remember browsing through some topics in serious discussion, I saw a couple of calculations at your hands. I was hoping you would come along! :D

That's what we math majors are for :P



?????

Aug 30 2009, 3:25 pm BeDazed Post #30



Look on first page >_< I want some credits too.
*rawrs



None.

Aug 30 2009, 3:40 pm ProtoTank Post #31



You did help as well, you did basically the same thing as clokr_, he just substituted. His method just clicked a little easier. Thanks for the contribution anyway!



I'm only here because they patched SC1 and made it free.

Aug 30 2009, 3:51 pm Bar Refaeli Post #32



I always thought factoring was 10x easier than the quadratic



None.

Aug 30 2009, 4:14 pm poison_us Post #33

Master has given Dobby a doctorate! Dobby is free!

Quote from name:Raccoon
I always thought factoring was 10x easier than the quadratic

I always thought the quadratic worked 10x as often as factoring :P




Aug 30 2009, 7:12 pm DT_Battlekruser Post #34



BeDazed solved it essentially the same as Clokr, so give him some credit :P



None.

Aug 30 2009, 7:31 pm Bar Refaeli Post #35



Quote from poison_us
Quote from name:Raccoon
I always thought factoring was 10x easier than the quadratic

I always thought the quadratic worked 10x as often as factoring :P
I rig my problems so I can factor. ^^



None.

Aug 30 2009, 8:07 pm Falkoner Post #36



Quote
your answer is wrong :/. I respect you as a forum member, but that is not the correct way to solve the problem graphically.

Woops, guess I plugged it into WinCalc wrong :P (although admittedly I should've been able to easily do that in my head..) All this logarithm and fractional exponents and such were done in 5/6 math last year, but I forgot it :P

Although I still don't understand why my way of solving doesn't work properly, it seems like it should get the answer.. :ermm:



None.

Aug 30 2009, 9:08 pm Syphon Post #37



Quote from name:Ultimo
Quote
log2(5-2x/2x) = -2x
You can't go from that to this:
Quote
-(5-2x)log2(2x) = -2x
At the very least, it would turn into log2(5-2x) - log2(2x)

I figured log(1/n) = -log(n), so why not? :P



None.

Aug 30 2009, 9:10 pm Syphon Post #38



Quote from Clokr_
Oh god, a solve my homework topic...

Anyway...

Quote
2^x + 2^(-x) = 5
When solving an exponential equation the simplest way is to get all the powers to look the same. In this case you got 2^x and 2^(-x) which can be easily converted to 1/2^x:

2^x + 1/2^x = 5

Now you do a = 2^x to get a standard equation:

a + 1/a = 5

You solve it for a:

(a²+1)/a = 5 -> a²+1 = 5a -> a² - 5a + 1 = 0
so a = (5ħsqrt(25-4))/2 = (5ħsqrt(21))/2
Since a = 2^x then 2^x = (5ħsqrt(21))/2 and thus x = log2 ((5ħsqrt(21))/2)
Solved ^^

I cannot believe I didn't think of solving via substitution.



None.

Aug 30 2009, 9:29 pm DT_Battlekruser Post #39



Quote
I figured log(1/n) = -log(n), so why not? :P

log(ax) = log(a) + log(x), not a*log(x).



None.

Aug 30 2009, 9:50 pm poison_us Post #40

Master has given Dobby a doctorate! Dobby is free!

Quote from name:Raccoon
Quote from poison_us
Quote from name:Raccoon
I always thought factoring was 10x easier than the quadratic

I always thought the quadratic worked 10x as often as factoring :P
I rig my problems so I can factor. ^^

You have me curious: what's x² + 21x + 85 = 0?




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