test tomorrow: solving log eqns, exponential eqns, etc

[marie 2010]

My Algebra 2 teacher is giving us a test tomorrow and I was out sick since Wednesday. I really have no idea how to do these so anyone who could help me I really be so happy. So can you explain to me how to do these and sorry there are somany....... I'm terrible at logarithums.

1. log2 ( 7x-80)-log2 x=3

so far I have 7x-8-x=3 and I'm fairly sure I have no clue what I am doing.

2. log6 n=1/2log6 64

3. log5 (y-12)+log5 (y+12)=2
I got (y-12)=(y+12)=2

4. 1/4=4^x+5
I put log1-log4=log4^x+5

5. 8^x-1=16^3x

and now the two word problems

6. The kemp's bought a cndominium for $85,000. assuming that the value of the condo will appreciate at most 5% a year, how much will the condo be worth in 5 years. the formula is y=a(1+r)^t I have no clue what this formula is even so ya.

7. The number of bacteriaB in a culture increases according to the equation B=B.e^kt. ( the point between b and e is a circle thingy) The culture starts with 400 bacteria and has 700 bacteria after 3hours. How many bacteria will there be after 12 hours.

Anyone who has any idea once again I would really love the help THANK YOU

 

[skeeter]

get some clues ...

http://www.purplemath.com/modules/solvelog.htm

 

[stapel]

I really have no idea how to do these...

If you missed the lessons, can't figure out the book or the class notes you got from a friend, and "have no idea how to do these" various exercises, then you'll need to start with lessons. Since we cannot replicate the missing hours of classroom instruction within this environment, you'll need to try online lessons. Fortunately, there are loads of great lessons available! :wink:

. . . . .Google results for "exponents"

. . . . .Google results for "exponential functions"

. . . . .Google results for "logarithms"

. . . . .Google results for "solving log equations"

. . . . .Google results for "solving exponential equations"

. . . . .Google results for "exponential word problems"

Allow yourself a few days to study and absorb the material. Work the examples in your text, and compare your results with what the book provides. And if you have some of the answers in the back, work those exercises, too, until you feel confident that you have a basic grasp of the material.

Then please attempt these exercises. If you get stuck, you will be able to reply with a clear listing of everything you have tried so far, and we'll be glad to try to help you get "un-stuck"!

Eliz.