Saturday, March 21, 2009

Log set 5

  1. Express the following as a single logarithm:1. log [3] 7 + log [3] 5
  2. log [2] 16 + 3log [2] 4 - log [2] 8
  3. log [5] 9 + log [5] 24.
  4. log [5] 5 + log [5] 10 - log [5] 3 = 0 3.4.

23 comments:

  1. problem 1:

    log [3] 7 + log [3] 5

    first you check to see if the logs are of the same base. if they are not of the same base, you make them both base 10.

    always remember that log[2] 8 = 3 is the same as 2^3 = 8,
    log a + log b = log a*b,
    log a - log b = log a/b.

    with those in mind you can appraoch to make the log question into one expression.

    log[3] 7*5

    ReplyDelete
  2. can #2 be worked out by dividing the equation by log 2

    ReplyDelete
  3. to answer your question "animechic"
    yes u can
    but first you have to get rid off the coefficient
    making the equation
    log[2]16 + log[2]4^3 - log[2]8

    hope this help

    ReplyDelete
  4. problem 3

    first there are no coefficient
    we notice the bases are the same
    so
    using the log rule
    log[a]b + log[a]c = log[a]bc

    the equation become

    log[5](9)(24)

    then using
    rule log[a]b = logb/loga

    we get log(9*24)/log5
    we solve for log
    then divide
    to get our answer

    ReplyDelete
  5. no 2

    'animechic' i dont think you can just divide by log 2. you have to know what opperations there are and then apply the log rules for them, this is what i mean:

    well 'Goldfinger' was right to say that the first thing to do is to remove cofficients:

    log[2]16 + log[2]4^3 - log[2] 8

    now from BODMAS we know that in this case we should add 1st, and we know from our log rules that when adding common logs we multiply:

    log[2](16*64) - log[2] 8

    we also know from our log rules that when subtracting common logs we divide:

    log[2](1024/8)

    log[2] 128

    ReplyDelete
  6. no 4
    for this problem the same principles apply as in no 2. these are 1)remove cofficients 2)when adding common logs, multiply 3)when subtracting common logs, divide.

    i think the equation is equal to 3.4, it looks like that so im using that, correct me if its something else:

    log[5] (5*10) - log[5] 3 = 3.4

    log[5] (50/3) = 3.4

    log[5] 16.6 = 3.4

    ReplyDelete
  7. log [3] 7 + log [3] 5
    log [3] (7*5)
    log [3] 35

    ReplyDelete
  8. Darky don't you have to solve out the question?

    ReplyDelete
  9. Or sorry i now saw the question asked to express not solve.

    ReplyDelete
  10. Question : Let logb(2) = 0.3869, logb(3) = 0.6131, and logb(5) = 0.8982. Using these values, evaluate logb(10).

    Since 10 = 2 × 5, then:

    logb(10) = logb(2 × 5) = logb(2) + logb(5)

    Since I have the values for logb(2) and logb(5), I can evaluate:

    logb(2) + logb(5) = 0.3869 + 0.8982 = 1.2851

    Then logb(10) = 1.2851.

    ReplyDelete
  11. Question : Let logb(2) = 0.3869, logb(3) = 0.6131, and logb(5) = 0.8982. Using these values, evaluate logb(9).

    Since 9 = 32, then:

    logb(9) = logb(32) = 2logb(3)

    Since I have the value for logb(3), then I can evaluate:
    2logb(3) = 2(0.6131) = 1.2262

    Then logb(9) = 1.2262.

    ReplyDelete
  12. QUESTION TO DO:

    Let logb(2) = 0.3869, logb(3) = 0.6131, and logb(5) = 0.8982. Using these values, evaluate logb(7.5).

    ReplyDelete
  13. question 1
    log[3] 7 + log[3] 5

    we realize they have sme base so therefore the answer will be:

    log[3]7*5

    ReplyDelete
  14. in no. 2 we have a 3 infront of the log so that indicates that we have to remove the 3 and put it as a power

    so the quetion will now read:
    log[2]16 + log[2]4*3 - log[2]8

    then we get 4 + 6 - 3 = 7

    ReplyDelete
  15. again in question 3, we have same bases so
    log[5]9 + log[5]24

    and the opperation in addition so we get
    log[5]9*24

    ReplyDelete
  16. Question 1
    log [3] 7 + log [3] 5
    they are the same bases so we multiply therefore we get

    log [3] (7*5)
    log [3] 35

    log 35/ log 3 = 1.46

    ReplyDelete
  17. Question 2
    log [2] 16 + 3log [2] 4 - log [2] 8

    firstly we work out the addition part of the question and sine the have the same base we multiply and we get

    log [2] 16 + log [2] 4^3 - log [2] 8
    log [2] 16 + log [2] 64 - log [2] 8
    log [2] (16*64) - log [2] 8
    log [2] 1024 - log [2] 8

    Now since it is subtraction and has the same base we divide and we get

    log [2] 1024 / 8
    log [2] 128

    log 128 /log 8 = 7

    ReplyDelete
  18. Question 3
    log [5] 9 + log [5] 24.

    The base are the same so we multiply because its addition

    log [5] (9 * 24)
    log [5] 216

    log 216 / log 5 = 3.34

    ReplyDelete
  19. For the log questions above always remember that when you are add two logs on with the same base, you multiply and when substracting, you devide...

    ReplyDelete
  20. 1)log [3] 7 + log [3] 5

    apply the rules of logs

    log a + log b = log a*b

    log 3 35

    ReplyDelete
  21. 3)log [5] 9 + log [5] 24

    apply the rules of logs

    log a + log b = log a*b

    log 5 24*9

    ReplyDelete
  22. log [2] 16 + 3log [2] 4 - log [2] 8

    in this question we are applying the rules of logs


    when adding and subtracting


    first thing remove all coefficients
    log [2] 16 + log [2] 64 - log [2] 8
    log [2] (16*64) - log [2] 8
    log [2] 1024 - log [2] 8

    now we apply the subtracting rule so we divide.

    log [2] 1024 / 8
    log [2] 128

    calculator dsent have base 2 so we use base convert to base 10


    log 128/ log 2 =

    ReplyDelete