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# Solve this? Watch

1. Does anybody know how to solve for ?

Thanks!
2. It's a cubic in (r+1). I can't see an obvious way to solve it, so multiply through, collect and factorise?

(Actually, cancelling the -5000 makes it a quadratic in (r+1), so use the formula if it doesn't factorise)
3. (Original post by SimonM)
It's a cubic in (r+1). I can't see an obvious way to solve it, so multiply through, collect and factorise?

(Actually, cancelling the -5000 makes it a quadratic in (r+1), so use the formula if it doesn't factorise)
Nope, I can't do it. I'm an economist (read: second-rate mathematician). Has anybody been able to do this?
4. Let u = (r+1) then multiply through by u^3. You'll get a quadratic in u (or r+1).
5. (Original post by dave_chapman)
Let u = (r+1) then multiply through by u^3. You'll get a quadratic in u (or r+1).
I don't know what that means. Can you show me?
6. - multiply by provided that r is not equal -1.

- now cancel out the identical bits on both sides:
- now get everything on one side of the equation
- now you can substitute (1+r) with u and solve this quadratic equation for u (u is not equal to 0)
7. Is this some sort of DCF?

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