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rjblayz rjblayz
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11 years ago
Ok. The equation I am stuck on is as follows: 50/(1+e^-x) = 4.
I need to solve for x. What do I do!? I've tried everything I can think of.. Thanks for your time.
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microbio24microbio24
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#1
11 years ago
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#2
11 years ago
1) Cross multiplying, 50 = 4(1 + e^-x) = 4 + 4*(e^-x)

2) ==> e^-x = 46/4 = 11.5

3) Taking natural log on both sides, -x = ln(11.5) = 2.3424

Hence x = -2.3424.
wrote...
#3
11 years ago
First you need to transform the equation so that it is calculator-ready.

50/(1 + e^-x) = 4

50 = 4(1 + e^-x)

50/4 = 1 + e^-x

(25/2) - 1 = 1/e^x

e^x = 1/((25/2) - 1)

x = ln(1/((25/2) - 1))

It is now calculator-ready.  Enter everything carefully.  Don't lose any parentheses.

The answer I got is -2.442347035
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