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Help with the Second Derivative of the Logisitic Function

Hi, I need to do the second derivative of the Logistic function in order to find the point of inflection. Unfortunately, for the life of me cannot do this in general terms.
The Logistic equation i am working with (like the values which I have, as in the constants) is as follows:

y=L/(1+Ae^-bx), where L,A, and b are positive constants.

Thanks for your time and help.
Original post by SwampMagic
Hi, I need to do the second derivative of the Logistic function in order to find the point of inflection. Unfortunately, for the life of me cannot do this in general terms.
The Logistic equation i am working with (like the values which I have, as in the constants) is as follows:

y=L/(1+Ae^-bx), where L,A, and b are positive constants.

Thanks for your time and help.


We can rewrite that as y=L(1+Ae−bx)−1y=L(1+Ae^{-bx})^{-1}

For the first derivative you just need the chain rule, and then for the second, chain rule and product rule will cover it.

Can you have a go and see what you get?

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