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Help with Logarithm questions.?

Question 1

http://i51.tinypic.com/2ms126s.gif

Question 2

http://i56.tinypic.com/35luvqb.gif

Could you please provide each step and a small explanation? Thanks.

Sorry I had to put in pictures. I didn't know how to write it here so I used an online equation editor.

1 Answer

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  • 1 decade ago
    Favorite Answer

    Q1:

    base change formula is: log(A) to the base B = log(A) to base y/ log(B) to base y (new base "y")

    therefore,

    log(32) base7 / log(8root2) base 7

    = log(32)/log(7) / log(8root2)/log(7) (to the new base, say "a"....it doesn't matter)

    =log(32)/log(8root2) ...........(log(7) gets cancelled)

    now 32 can be written as 2x2x2x2x2 which is (root2)^10

    also 8root2 can be similarly written as 2x2x2xroot2 which is (root2)^7

    now by formula log(A^X) = X log(A), we get

    log(32)/log(8root2)

    = log [(root2)^10)] / log [(root2)^7]

    = 10 log(root2) / 7 log(root2)

    log (root2) gets cancelled

    = 10/7.

    Q2:

    log (XY) = log(X) + log(Y)

    log (X/Y) = log(X) - log(Y)

    therefore we get

    log [(18x12)/125] / log [42/35]

    now rewriting 18x12 as 6^3, 125 as 5^3 and 42/35 as 6/5, we get

    log [(6/5)^3] / log[6/5]

    = 3 log[6/5] / log[6/5]

    = 3.

    hope the answers are right. pls check them. but im sure about the methods.

    hope this helped you.

    Source(s): check http://en.wikipedia.org/wiki/List_of_logarithmic_i... for the basic identities....
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