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# Core 3 logs! Watch

1. Does anybody know how to dothis question?

Given that

ln (2x^2 + 9x? 5) = 1 + ln (x^2 + 2x ?15), x ? ?5,

(b) find x in terms of e.
2. (Original post by stanmoor)
Does anybody know how to dothis question?

Given that

ln (2x^2 + 9x? 5) = 1 + ln (x^2 + 2x ?15), x ? ?5,

(b) find x in terms of e.
What are the question marks? Also, what exactly have you tried?
3. Think about log rules.
4. Before posting things like this can you make sure your notations are correct...? It can't have been hard to spot question marks which don't make sense, right?
5. Sorry, calm down!
ln (2x^2 + 9x? 5) = 1 + ln (x^2 + 2x ?15)

I have tried doing ln(2x^2 + 9x -5) - ln(x^2 + 2x - 15) = 1

This makes ln (2x^2 + 9x - 5 / x^2 + 2x - 15) = 1

Then is it right to e each side?
6. (Original post by stanmoor)
Sorry, calm down!
ln (2x^2 + 9x? 5) = 1 + ln (x^2 + 2x ?15)

I have tried doing ln(2x^2 + 9x -5) - ln(x^2 + 2x - 15) = 1

This makes ln (2x^2 + 9x - 5 / x^2 + 2x - 15) = 1

Then is it right to e each side?
You could do it that way yes But please do double check you don't replace minus signs with question marks next time
7. I have done that,
and now i have:

2x -1 / x - 3 = e

How would i get x on its own??
8. (Original post by stanmoor)
I have done that,
and now i have:

2x -1 / x - 3 = e

How would i get x on its own??
Times both sides by (x-3) then put every thing with x in it on one side

So you'll get: x times SOMETHING = SOMETHING ELSE
and divide by the something
9. (Original post by stanmoor)
I have done that,
and now i have:

2x -1 / x - 3 = e

How would i get x on its own??

10. Thanks alot !! Very helpful
11. (Original post by stanmoor)
I have done that,
and now i have:

2x -1 / x - 3 = e

How would i get x on its own??
should be a simple rearrangement for you. Since this fraction is still essentially a fraction, you should treat the problem like any other fraction.

For example, like how you would treat . By multiplying both sides by the numerator, 2, you eliminate the fraction on the left hand side and you end up with .

Remember that e is just a number, and is your friend.

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Updated: December 24, 2010
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