in reply to Re^2: Internal Rate of Return
in thread Internal Rate of Return

As long as the one positive payment follows all of the negative payments, I guarantee that you only have one positive real root. See Re^2: Internal Rate of Return for proof. (I have the signs the other way there, but it is easy to switch them.)

Incidentally a leading payment of 0 is handled by dropping all of the payments of 0. Then either you have no payments, or you've got a leading payment that isn't 0.

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Re^4: Internal Rate of Return
by ig (Vicar) on May 20, 2009 at 02:05 UTC

    I'll have to look up bijection, but I follow your explanation of the conversion and I can understand that if all but the first coefficient are positive then the derivative is always positive so there can be only one zero. That confirms my suspicion - Thanks!!

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