logarithms

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gcfan4life1023

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I dont understand this at all and I have a few days before the mid-term please somebody help me
Given ln(x) = 5 solve for x how do i even begin

Also given e^4x= 12 solve for x wouldnt x =3 i don't know somebody please help me and please try to give me an explanation im so confused
 
gcfan4life1023 said:
I dont understand this at all and I have a few days before the mid-term please somebody help me
Given ln(x) = 5 solve for x how do i even begin
Click to expand...
You do NOT begin. You simply finish by applying the definition.

ln(x) = 5 MEANS \(\displaystyle \L e^{5} = x\)

And you're done.

Also given e^4x= 12 solve for x wouldnt x =3
Click to expand...
Why? Have you been studying AT ALL?
 
From what you've posted, it looks like your pre-calculus algebra class didn't cover logs or exponentials at all, and your calculus class hasn't reviewed the material.

Would you like us to try to find online lessons covering these topics, so you can get the necessary "background" material that your calculus class is (apparently) expecting you to have?

Thank you.

Eliz.
 
we don't learn in my calculus class he just tells us read this section and do these problems and he doesn't really explain anything so I have no clue how to start that i know that ln stands for natural log but that's all i know im so confused and we are reviewing this stuff for midterms and i dont understand it thanks for everyone's help though I didnt take a pre-calculus class We just go straight from algebra 3 and trigonometry in my school to what they call calculus
 
"Algebra 3 and Trigonometry" was your "pre-calculus" class; they just didn't call it "pre-calc". But how they never got around to mentioning logs or exponentials, I can't begin to guess. :shock:

Here are some lessons that should go some way toward giving you the necessary background information:

. . . . .Karl's Calculus: Exponentials and Logarithms

. . . . .BBC Education: Exponentials and Logarithms

. . . . .Paul's Online Math Notes: Exponentials / Logarithms

. . . . .Exponentials series

. . . . .Logarithms series

Hope these help a bit!

Eliz.
 
Ok wait so to solve for ln(x)= 5 do i just type that in my calculator to get a decimal approximation
 
gcfan4life1023 said:
...to solve for ln(x)= 5 do i just type that in my calculator to get a decimal approximation
Click to expand...
There could be a method for using the calculator to obtain a decimal approximation to the answer. Are you supposed to approximate?

Eliz.
 
I figured out both my problems thanks so much
for the problem solve for x given e^4x= 12
x equals ln(12)/ 4 because you take the ln on both sides and switch the 4x out to the front to get 4x ln e =ln 12 and then ln times e equals one so i get 4x = ln 12
then i divide both sides by 4 to get x= ln12/4 because u cant divide the 12 by 4 because it is with the natural log I forgot about that rule Thanks for everyone's help
and then for given ln(x)= 5 solve for x
x = e^5 thanks for the help I think i am finally beginning to understand this
 
1) e<sup>4x</sup> = 12

Your answer: x = ln(12)/4

. . . . .Correct!

2) ln(x) = 5

Your answer: x = e<sup>5</sup>

. . . . .Correct!

Excellent! :D

Eliz.
 
actually i got the ln(x)= 5 and the answer e^5 from one of the posts I just figured out why it was correct I dont want to take credit for that answer because i didnt solve it I had help Thanks again everyone Since all of my questions are now solved. I think i will do well on next weeks midterm I just gotta wait to see what else we review in class yet and then ill know how well i will do. Thannks again for everyones help
 
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