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Logarithmic Equations - HSN forum

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Logarithmic Equations


9 replies to this topic

#1 scotland_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)

#2 bred

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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. sad.gif
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#3 Shaun

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Posted 03 March 2005 - 09:57 PM

[attachmentid=49]

Hope this helps!

#4 Shaun

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Posted 04 March 2005 - 05:14 PM

Can anybody tell me if I'm right?

lol

#5 sparky

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Posted 04 March 2005 - 06:21 PM

It looks correct to me!
Mark

#6 scotland_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.

#7 George

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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.

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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.

#8 Shaun

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Posted 04 March 2005 - 08:31 PM

So it's log to the base seven?

#9 George

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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?

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

#10 Dave

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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

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