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Logarithmic Equations - HSN forum

# Logarithmic Equations

9 replies to this topic

### #1scotland_2004

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Posted 03 March 2005 - 06:44 PM

Hey, I was wondering if anyone could help me with this question:

Solve for x larger than 0,
log7(x2-1) - log7(x-1) = 2

Thanks!
(Its x squared in the bracket)

### #2bred

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Posted 03 March 2005 - 07:07 PM

I'm sorry I can't help you but I'd just like to say logs are important! I'm sure the 7 mark log question in last year's exam cost me a grade B (I got a C) - and in turn probably an unconditional offer or two for uni! Oh and the 4 marker question that I didn't recognise where you use the easy peasy discriminant formula.
Please vote for me! (Brendan Howard, 5th from bottom, only 1 vote required): http://answers.polld...m/poll/2330393/

### #3Shaun

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Posted 03 March 2005 - 09:57 PM

[attachmentid=49]

Hope this helps!

### #4Shaun

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Posted 04 March 2005 - 05:14 PM

Can anybody tell me if I'm right?

lol

### #5sparky

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Posted 04 March 2005 - 06:21 PM

It looks correct to me!
Mark

### #6scotland_2004

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Posted 04 March 2005 - 06:36 PM

Hey, Thanks for your help! I think that is one way to do it because we did that kind of stuff today in class but my teacher said that it was a non-calculator question so the answer was x=48 in the end.

### #7George

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Posted 04 March 2005 - 07:56 PM

QUOTE(scotland_2004 @ Mar 4 2005, 06:36 PM)
Hey, Thanks for your help! I think that is one way to do it because we did that kind of stuff today in class but my teacher said that it was a non-calculator question so the answer was x=48 in the end.

I think that's because the question is probably log7(x2-1) - log7(x-1) = 2, not with loge which is what Shaun solved.

The working Shaun provided is right though; the solution will end up as 72 = x + 1, so x = 48.

### #8Shaun

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Posted 04 March 2005 - 08:31 PM

So it's log to the base seven?

### #9George

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Posted 05 March 2005 - 06:08 PM

QUOTE(fearfactor47 @ Mar 4 2005, 08:31 PM)
So it's log to the base seven?

I think so, since that agrees with the answer given by the teacher. The working you done for loge was all correct though

### #10Dave

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Posted 05 March 2005 - 07:15 PM

i think I should remind people that they can format their posts using BB Code. For help inoformation you can look click the "BB Code help" under the clickable smilies when you add a post

If i am not here i am somewhere else

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