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# Basic log evaluation difficulty

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1. Hello everyone,

I'm having problems understanding how to correctly evaluate the following;

log2 (1/8)

I obviously have to find x, and I got as far as this;

1/8 = 2x

8-1= 2x

It's quite frustrating trying to understand something that seems quite simple, any help pushing my understanding of this would be very welcome.
2. (Original post by Brainfrozen)
Hello everyone,

I'm having problems understanding how to correctly evaluate the following;

log2 (1/8)

I obviously have to find x, and I got as far as this;

1/8 = 2x

8-1= 2x

It's quite frustrating trying to understand something that seems quite simple, any help pushing my understanding of this would be very welcome.
What you have done so far looks correct, so the next thing to do would be to try to change the LHS into a power of 2 so you can equate the powers (since the base would be the same). Therefore you need to change 8 into a power of two first. Can you go from there?
3. (Original post by solC)
What you have done so far looks correct, so the next thing to do would be to try to change the LHS into a power of 2 so you can equate the powers (since the base would be the same). Therefore you need to change 8 into a power of two first. Can you go from there?
Hi SolC

(23)-1=2x

4. Ah wait, is the answer -3?
5. (Original post by Brainfrozen)
Ah wait, is the answer -3?
(Original post by Brainfrozen)
Hi SolC

(23)-1=2x

Thats right yeah, but remember now you have to use one of the index rules before you can equate the powers
6. (Original post by Brainfrozen)
Ah wait, is the answer -3?
yeah thats right
7. (Original post by solC)
yeah thats right
Thanks solC, I'm very rusty with indices and logs, just getting to grips with them again.

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