Logarithms

[n2Ryan]

Can anyone explain to me why I keep getting this wrong? I have 2 answers here and it says they're both wrong...
Ln(a)=2
Ln(b)=3
Ln(c)=5

 

[Dr.Peterson]

Your second line is wrong. Try taking that part more slowly (that is, write more steps) so you can check each step.

Be especially careful with signs, of course. When you say you have two answers, it looks like you mean that you tried making one sign either positive or negative; you shouldn't be guessing at that point! But the real problem is earlier.

 

[pka]

Can anyone explain to me why I keep getting this wrong? I have 2 answers here and it says they're both wrong...
Ln(a)=2
Ln(b)=3
Ln(c)=5

Is the first them \(\displaystyle \ln(c^{-1})\) is it \(\displaystyle [\ln(c)]^{-1}\)

 

[n2Ryan]

Is the first them \(\displaystyle \ln(c^{-1})\) is it \(\displaystyle [\ln(c)]^{-1}\)

Ln(c^-1)

 

[Dr.Peterson]

The part that makes me curious is [MATH]\frac{a}{b^1}[/MATH]. Why would the 1 be written?

But have you considered my comment yet? You changed [MATH]\left(\ln\frac{a}{b^1}\right)^{-2}[/MATH] to [MATH]\ln\left(a^{-2}\right) - \ln\left(b^{2}\right)[/MATH], which is wrong.

I'd just simplify inside the parentheses, then do your substitutions with the given ln values.

 

[pka]

Can anyone explain to me why I keep getting this wrong? I have 2 answers here and it says they're both wrong...
Ln(a)=2
Ln(b)=3
Ln(c)=5

Assuming that I have read your grouping correctly, here is my take.
\(\displaystyle \begin{align*}\ln(c^{-1})&=-\ln(c) \\&=-5 \end{align*}\)_______ \(\displaystyle \begin{align*}\ln\left(\frac{a}{b}\right)&=\ln(a)-\ln(b) \\&=(2)-(3)\\&=-1\end{align*}\)_______ \(\displaystyle \left[\ln\left(\frac{a}{b}\right)\right]^{-2}=[-1]^{-2}=1\)

 

[Steven G]

If you take away 4 cookies and then you take away 6 cookies, THEN you took away 10 cookies. That is -4 - 6 = -10 so -4 + 6 can't be -10!! After all if you took away 4 cookies and put back 6 cookies (so -4 + 6) there are two more cookies then you started with, ie -4+6=2

 

[pka]

If you take away 4 cookies and then you take away 6 cookies, THEN you took away 10 cookies. That is -4 - 6 = -10 so -4 + 6 can't be -10!! After all if you took away 4 cookies and put back 6 cookies (so -4 + 6) there are two more cookies then you started with, ie -4+6=2

Jomo, which posting are you answering? It would be most helpful if we all quoted the posts to which we are responding.

 

[Steven G]

Jomo, which posting are you answering? It would be most helpful if we all quoted the posts to which we are responding.

Post number 1 where the OP was not sure what -4+6 equals.
I agree with you that I reply to the post I am answering. It is just so easy to not to do that with this format

 

[n2Ryan]

If you take away 4 cookies and then you take away 6 cookies, THEN you took away 10 cookies. That is -4 - 6 = -10 so -4 + 6 can't be -10!! After all if you took away 4 cookies and put back 6 cookies (so -4 + 6) there are two more cookies then you started with, ie -4+6=2

I got -10 because i multiplied -5(2)...

 

[n2Ryan]

The part that makes me curious is [MATH]\frac{a}{b^1}[/MATH]. Why would the 1 be written?

But have you considered my comment yet? You changed [MATH]\left(\ln\frac{a}{b^1}\right)^{-2}[/MATH] to [MATH]\ln\left(a^{-2}\right) - \ln\left(b^{2}\right)[/MATH], which is wrong.

I'd just simplify inside the parentheses, then do your substitutions with the given ln values.

Im not sure why it has the 1 there but thats what the problem says in my assignment. Im just going by what it said... its probably just to throw me off. Anyway, thank you!

 

[n2Ryan]

The correct answer was -5...

Just to update u guys, i did eventually get it! Thanks for all the input!

 

[Steven G]

I got -10 because i multiplied -5(2)...

Not true, sorry. You had two solutions (remember?) one went as follows: -5(-4+6) = (-5)(2) = -10 and the other solution you had came from -5(-4+6) = (-5)(10) = -50. So you had two results for -4+6. You had 2 and 10!

 

[n2Ryan]

Not true, sorry. You had two solutions (remember?) one went as follows: -5(-4+6) = (-5)(2) = -10 and the other solution you had came from -5(-4+6) = (-5)(10) = -50. So you had two results for -4+6. You had 2 and 10!

I'm sorry, are you trying to attack me when I was simply asking for help on a math problem? I know what I wrote and posted but that wasn't the end of me trying to solve the problem. If you're going to be ugly about a learning opportunity for me, then please refrain from commenting.

To clear up what I wrote, it was originally (-5)(-4-6)=(-5)(-10)=50 then I crossed out the (-) and changed it to (+). Which is why it then said (-5)(-4+6)=(-5)(2)=-10. Hence why I had 2 different answers. So now that we have the simpler math out of the way, if you wish to comment more, why don't you add something useful instead of being a jerk?

 

[Steven G]

I'm sorry, are you trying to attack me when I was simply asking for help on a math problem? I know what I wrote and posted but that wasn't the end of me trying to solve the problem. If you're going to be ugly about a learning opportunity for me, then please refrain from commenting.

To clear up what I wrote, it was originally (-5)(-4-6)=(-5)(-10)=50 then I crossed out the (-) and changed it to (+). Which is why it then said (-5)(-4+6)=(-5)(2)=-10. Hence why I had 2 different answers. So now that we have the simpler math out of the way, if you wish to comment more, why don't you add something useful instead of being a jerk?

I'm sorry that you think I was being a jerk. That was not my intention.