Posted by **BecKi** on Sunday, February 21, 2010 at 7:32am.

medication duration using the function of e through time lapse

problem D(h)=8e(up carrot)-0.31(h)

find med level at 1 hour- no problem 5.88mg. but every time I insert 4 for the 4 hours I get a larger number... much larger indicting the med level has gone up.

I am sure it is my bad math not the patient begining kidney failure. any help would be apprecitated.

bjm

- Pre-Calc -
**Reiny**, Sunday, February 21, 2010 at 7:53am
When h = 4 I get D(4 = 2.315

must be the way you are entering the values for calculations on your calculator.

On mine, an old "Sharp", I did:

2ndF

ln

(±.31x4)

=

x

8

=

- Pre-Calc -
**MathMate**, Sunday, February 21, 2010 at 8:00am
It helps to find the problem if you posted what you've got, even if the number is much larger.

If you are using a calculator, I suspect the "minus" sign before the 0.31 had been left out.

The given formula is:

D(h) = 8e^{-0.31h}

For h=1, 5.87 is correct.

For h=4,

8e^{-0.31*4}

=8e^{-1.24}

=2.32

If the minus sign is left out, it would have given 27.64 instead.

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