Logs

[khris le]

Hi can someone help me with these please. I've never done logs before and this is stressing me out so much. My classes are going by so quickly and youtube isn't helping me much. Are there any channels anyone would recommend?



How do I proceed with these questions, I don't know what to do

 

[Steven G]

I will give you two hints.
1) If two times something equals four, what does the something equal.
2) log_aB=C is equivalent to a^C=B

 

[khris le]

I will give you two hints.
1) If two times something equals four, what does the something equal.
2) log_aB=C is equivalent to a^C=B

i'm mathematically dumb

 

[Steven G]

If 2 x (something) = 4, then the something must equal ...
Example: If 5x(something)=20, then the something MUST equal 4 only because 5x4=20.
Problem (a): Now what must log₈(2x-5) equal. Then use hint 2
Problem (b): Your work so far is correct. Use hint 2 above.

 

[Otis]

Hi khris. The first line of exercise (a) has 4 on the right-hand side of the equation, but then changes to 9 on the third line. That's from a mistake in line 2, where you thought you could add five to what's on the inside of the parentheses. The expression (2x-5) is what we call the logarithm's argument. We can't add to or subtract from that expression while it's part of the logarithm. So, your first step ought to be dividing each side of the given equation by 2.

If your class seems to be going too fast, then you might not have been assigned enough practice (for memorizing basic definitions and properties). That's a common problem these days – especially with online courses. Another issue could be that you've forgotten some prerequisite material for learning logarithms.

Do you understand powers? For example, the following expressions are powers (the first is a power of 3, the second is a power of 16). Do you know how to determine their values?

3⁴

16^1/4

If the expressions above are easy for you to calculate, then check out this link to some introductory material for logarithms.