Log problem: solve 525 / (1 + e^(-x)) = 275 and check

[kryms3n]

In this Exercise, solve the exponential equation algebraically. Round your result to three decimal places. Check if your answer if correct

525 / (1 + (e^-x)) = 275

Can you solve it?

 

[tkhunny]

I wish I could see your work. I already know how to solve it. Your thread title suggests how to proceed. Give it a go.

Hint:

\(\displaystyle \L\;\frac{1+e^{-x}}{525}\;=\;\frac{1}{275}\)

 

[mark]

525/(+e^-x) = 275

cross multiply

525 = 275(1+e^-x)


525/275 = 1+ e^-x


525/ 275 - 1 = e^-x

e^-x is the same thing as 1/e^x

525/275 - 1 = 1/e^x

10/11 = 1/e^x

cross mulitiply again

10e^x = 11

e^x = 11/10

take ln on both sides because the base of ln is e
and thus ln e^x = x

so x = ln 11/10

 

[stapel]

Can you solve it?

Of course we can. But the purpose of this tutoring-help site is not to prove our own prowess; it's to help students. Please help us help you by showing what you have tried and how far you have gotten.

Thank you.

Eliz.

 

[tkhunny]

cross multiply
cross mulitiply again

There is no such process. You can multiply bopth sides of an equation by the same non-zero value, if you like. Why not just multiply, instead of inventing some trick.

I'm not seeing where you are struggling, except that you are not adding enough explanation of what you are doing.