# Problem with exponential question

• Jun 23rd 2013, 04:12 AM
pumbaa213
Problem with exponential question
Given that lnx =1.5 and ln√y =2.2 , evaluate

(i)
http://latex.codecogs.com/gif.latex?...t%7By%7D%7D%29

(ii) 2x-y

The answer given is (i) 0.781 but i cant seem to get it.

For part (ii), im not sure how to even start.
Could somebody help me with this?

Thank you very much!
• Jun 23rd 2013, 04:24 AM
Plato
Re: Problem with exponential question
Quote:

Originally Posted by pumbaa213
Given that lnx =1.5 and ln√y =2.2 , evaluate
(i)
http://latex.codecogs.com/gif.latex?...t%7By%7D%7D%29

(ii) 2x-y

$\sqrt{\ln(ex)}=\sqrt{\ln(e)+\ln(x)}=\sqrt{2.5}$ Do you know why?

$\ln(y)=4.4$ Do you know why?
• Jun 23rd 2013, 04:32 AM
pumbaa213
Re: Problem with exponential question
Okay i got the first part thanks alot! :) its so much easier when someone dissects it for you.
How about (ii) 2x - y

How should i start?

thank you!
• Jun 23rd 2013, 04:34 AM
grillage
Re: Problem with exponential question
You could start by putting x and y in simple terms. So:

$lnx=1.5 \textup{ so }x=e^{1.5}$

$ln\sqrt{y}=2.2$

$ln(y^{\frac{1}{2}})=2.2$

$\frac{1}{2}lny=2.2 \textup{ so }y=e^{4.4}$
• Jun 23rd 2013, 04:46 AM
pumbaa213
Re: Problem with exponential question
yess! finally got the answer. Thank you plato and grillage! :)