Random algebra Q

[Fyrefly]

I am phail maths now... it's been too long... can anyone solve for i for me?

3605 = (1000/i)[1-(1+i)^-5]

(I am phail @ Latex as well)


Edit: The answer is supposed to be 12

[EvangelionZeta]

Expand:
3605=1000-1000(1+i)^(-5)
2605=-1000(1+i)^(-5)
-2.605=(1+i)^-5
-1/2.605=(1+i)^5
(-1/2.605)^(1/5)=1+i
(-1/2.605)^(1/5)-1=i

...somehow it doesn't look right, but that's roughly how I would have done it.

[Lighties]

Expand:
3605=1000-1000(1+i)^(-5)
2605=-1000(1+i)^(-5)
-2.605=(1+i)^-5
-1/2.605=(1+i)^5
(-1/2.605)^(1/5)=1+i
(-1/2.605)^(1/5)-1=i

...somehow it doesn't look right, but that's roughly how I would have done it.

Just pointing out that you expanded wrong in the first step - the first bracket is (1000/i), not just 1000.

I tried doing it by hand and got nowhere. Typed it into my calculator and after a 5 minute wait got that i was 0.119975? 

[EvangelionZeta]

...no wonder.  I read the 1000/i as 1000/1 and was thinking "wtf".  

-shamed-

Also hi Vicky.

[Lighties]

If it helps, I simplified it down to (200-721i)(1+i)^5=200. But that's about it. D:

You should be ashamed. And hello. (:

[Fyrefly]

Expand:
3605=1000-1000(1+i)^(-5)
2605=-1000(1+i)^(-5)
-2.605=(1+i)^-5
-1/2.605=(1+i)^5
(-1/2.605)^(1/5)=1+i
(-1/2.605)^(1/5)-1=i

...somehow it doesn't look right, but that's roughly how I would have done it.

Just pointing out that you expanded wrong in the first step - the first bracket is (1000/i), not just 1000.

I tried doing it by hand and got nowhere. Typed it into my calculator and after a 5 minute wait got that i was 0.119975? 

Well, that's the answer... it's actually an equation from my financial accounting textbook... the answer is 12%... so I guess at least the calculator can figure it out..?

I think I'm going to put this in my "too hard" pile.

Thanks for the help anyway guys!

[Lighties]

Haha, sorry I couldn't help more. But you're quite welcome. (: